Vectors comprising nucleic acids encoding anti-OX40 antibodies

ABSTRACT

The present disclosure provides antibodies that specifically bind to human OX40 receptor (OX40) and compositions comprising such antibodies. In a specific aspect, the antibodies specifically bind to human OX40 and modulate OX40 activity, e.g., enhance, activate, or induce OX40 activity, or reduce, deactivate, or inhibit OX40 activity. The present disclosure also provides methods for treating disorders, such as cancer, by administering an antibody that specifically binds to human OX40 and modulates OX40 activity, e.g., enhances, activates, or induces OX40 activity. Also provided are methods for treating autoimmune or inflammatory diseases or disorders, by administering an antibody that specifically binds to human OX40 and modulates OX40 activity, e.g., reduces, deactivates, or inhibits OX40 activity.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/384,116, filed Apr. 15, 2019, which is a division of U.S. patentapplication Ser. No. 15/148,720, filed May 6, 2016, now U.S. Pat. No.10,259,882, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/323,458, filed Apr. 15, 2016; 62/262,373, filedDec. 2, 2015; 62/161,198, filed May 13, 2015; and 62/158,515, filed May7, 2015, the entire disclosures of which are hereby incorporated hereinby reference in their entirety.

SEQUENCE LISTING

The instant application contains a sequence listing which has beensubmitted electronically in ASCII format and is hereby incorporated byreference in its entirety (said ASCII copy, created on Feb. 2, 2020, isnamed 701925_AGBW-132DIVCON_ST25.txt and is 121,015 bytes in size).

1. FIELD

The present disclosure relates to antibodies that specifically bind tohuman OX40 receptor (“OX40”), compositions comprising such antibodies,and methods of producing and using antibodies that specifically bind toOX40.

2. BACKGROUND

The contributions of the innate and adaptive immune response in thecontrol of human tumor growth are well-characterized (Vesely M D et al.,(2011) Annu Rev Immunol 29: 235-271). As a result, antibody-basedstrategies have emerged that aim to enhance T cell responses for thepurpose of cancer therapy, such as targeting T cell expressedstimulatory receptors with agonist antibodies, or inhibitory receptorswith functional antagonists (Mellman I et al., (2011) Nature 480:480-489). Antibody-mediated agonist and antagonist approaches have shownpreclinical, and more recently clinical, activity. An importantstimulatory receptor that modulates T cell, Natural Killer T (NKT) cell,and NK cell function is the OX40 receptor (also known as OX40, CD134,TNFRSF4, TXGP1L, ACT35, and ACT-4) (Sugamura K et al., (2004) Nat RevImmunol 4: 420-431). OX40 is a member of the tumor necrosis factorreceptor superfamily (TNFRSF) and signaling via OX40 can modulateimportant immune functions.

OX40 can be upregulated by antigen-specific T cells following T cellreceptor (TCR) stimulation by professional antigen presenting cells(APCs) displaying MHC class I or II molecules loaded with a cognatepeptide (Sugamura K et al., (2004) Nat Rev Immunol 4: 420-431). Uponmaturation APCs such as dendritic cells (DCs) upregulate stimulatory B7family members (e.g., CD80 and CD86), as well as accessoryco-stimulatory molecules including OX40 ligand (OX40L), which help tosculpt the kinetics and magnitude of the T cell immune response, as wellas effective memory cell differentiation. Notably, other cell types canalso express constitutive and/or inducible levels of OX40L such as Bcells, vascular endothelial cells, mast cells, and in some instancesactivated T cells (Soroosh P et al., (2006) J Immunol 176: 5975-5987).OX40:OX40L co-engagement is believed to drive the higher orderclustering of receptor trimers and subsequent signal transduction(Compaan D M et al., (2006) Structure 14: 1321-1330).

OX40 expression by T cells within the tumor microenvironment has beenobserved in murine and human tumor tissues (Bulliard Y et al., (2014)Immunol Cell Biol 92: 475-480 and Piconese S et al., (2014) Hepatology60: 1494-1507). OX40 is highly expressed by intratumoral populations ofregulatory T cells (Tregs) relative to conventional T cell populations,a feature attributed to their proliferative status (Waight J D et al.,(2015) J Immunol 194: 878-882 and Bulliard Y et al., (2014) Immunol CellBiol 92: 475-480). Early studies demonstrated that OX40 agonistantibodies were able to elicit tumor rejection in mouse models (WeinbergA D et al., (2000) J Immunol 164: 2160-2169 and Piconese S et al.,(2008) J Exp Med 205: 825-839). A mouse antibody that agonizes humanOX40 signaling has also been shown to enhance immune functions in cancerpatients (Curti B D et al., (2013) Cancer Res 73: 7189-7198).

OX40 and OX40L interactions also have been associated with immuneresponses in inflammatory and autoimmune diseases and disorders,including mouse models of asthma/atopy, encephalomyelitis, rheumatoidarthritis, colitis/inflammatory bowel disease, graft-versus-host disease(e.g., transplant rejection), diabetes in non-obese diabetic mice, andatherosclerosis (Croft M et al., (2009) Immunol Rev 229(1): 173-191, andreferences cited therein). Reduced symptomatology associated with thediseases and disorders has been reported in OX40- and OX40L-deficientmice, in mice receiving anti-OX40 liposomes loaded with a cytostaticdrug, and in mice in which OX40 and OX40L interactions were blocked withan anti-OX40L blocking antibody or a recombinant OX40 fused to the Fcportion of human immunoglobulin (Croft M et al.; Boot E P J et al.,(2005) Arthritis Res Ther 7: R604-615; Weinberg A D et al., (1999) JImmunol 162: 1818-1826). Treatment with a blocking anti-OX40L antibodywas also shown to inhibit Th2 inflammation in a rhesus monkey model ofasthma (Croft M et al.; Seshasayee D et al., (2007) J Clin Invest 117:3868-3878). Additionally, polymorphisms in OX40L have been associatedwith lupus (Croft M et al.).

Given the role of human OX40 in modulating immune responses, providedherein are antibodies that specifically bind to OX40 and the use ofthese antibodies to modulate OX40 activity.

3. SUMMARY

In one aspect, provided herein are antibodies that specifically bind toOX40 (e.g., human OX40).

In one embodiment, an antibody that specifically binds to OX40 comprisesa heavy chain variable region (VH) CDR1 comprising the VH CDR1 in SEQ IDNO: 16, a VH CDR2 comprising the VH CDR2 in SEQ ID NO: 16, a VH CDR3comprising the VH CDR3 in SEQ ID NO: 16, a light chain variable region(VL) CDR1 comprising the VL CDR1 in SEQ ID NO: 15, a VL CDR2 comprisingthe VL CDR2 in SEQ ID NO: 15, and a VL CDR3 comprising the VL CDR3 inSEQ ID NO: 15, wherein each CDR is defined in accordance with the Kabatdefinition, the Chothia definition, the combination of the Kabatdefinition and the Chothia definition, the IMGT numbering system, theAbM definition, or the contact definition of CDR.

In one embodiment, an antibody that specifically binds to OX40 comprises(a) a heavy chain variable region comprising a heavy chaincomplementarity determine region 1 (CDR1) comprising the amino acidsequence of GSAMH (SEQ ID NO: 4); a heavy chain CDR2 comprising theamino acid sequence of RIRSKANSYATAYAASVKG (SEQ ID NO: 5); and a heavychain CDR3 comprising the amino acid sequence of GIYDSSGYDY (SEQ ID NO:6); and (b) a light chain variable region comprising a light chain CDR1comprising the amino acid sequence of RSSQSLLHSNGYNYLD (SEQ ID NO: 1); alight chain CDR2 comprising the amino acid sequence of LGSNRAS (SEQ IDNO: 2); and a light chain CDR3 comprising the amino acid sequence ofMQALQTPLT (SEQ ID NO: 3).

In one embodiment, an antibody that specifically binds to OX40 comprises(a) a heavy chain variable region comprising a heavy chain CDR1comprising the amino acid sequence of GFTFSGSA (SEQ ID NO: 47); a heavychain CDR2 comprising the amino acid sequence of IRSKANSYAT (SEQ ID NO:48); and a heavy chain CDR3 comprising the amino acid sequence ofTSGIYDSSGYDY (SEQ ID NO: 49); and (b) a light chain variable regioncomprising a light chain CDR1 comprising the amino acid sequence ofQSLLHSNGYNY (SEQ ID NO: 44); a light chain CDR2 comprising the aminoacid sequence of LGS (SEQ ID NO: 45); and a light chain CDR3 comprisingthe amino acid sequence of MQALQTPLT (SEQ ID NO: 46).

In one embodiment, the antibody comprises a heavy chain variable regionhaving human or human derived framework regions.

In one embodiment, the antibody comprises a heavy chain variableframework region that is derived from an amino acid sequence encoded bya human gene, wherein said amino acid sequence comprises IGHV3-73*01(SEQ ID NO: 19).

In one embodiment, the antibody comprises a light chain variablesequence having human or human derived framework regions.

In one embodiment, the antibody comprises a light chain variableframework region that is derived from an amino acid sequence encoded bya human gene, wherein said amino acid sequence comprises IGKV2-28*01(SEQ ID NO: 18).

In one embodiment, the antibody comprises a heavy chain variable regionsequence comprising the amino acid sequence of SEQ ID NO: 16.

In one embodiment, the antibody comprises a heavy chain sequencecomprising an amino acid sequence selected from the group consisting ofSEQ ID NOs: 21, 23, 51, and 52. In one embodiment, the antibodycomprises a heavy chain sequence comprising an amino acid sequenceselected from the group consisting of SEQ ID NOs 60-63.

In one embodiment, the antibody comprises a light chain variable regionsequence comprising the amino acid sequence of SEQ ID NO: 15.

In one embodiment, the antibody comprises a light chain sequencecomprising the amino acid sequence of SEQ ID NO: 20.

In one embodiment, an antibody that specifically binds to OX40 comprisesa heavy chain variable region and a light chain variable region, whereinthe heavy chain variable region comprises the amino acid sequence of SEQID NO: 16.

In one embodiment, an antibody that specifically binds to OX40 comprisesa heavy chain variable region and a light chain variable region, whereinthe light chain variable region comprises the amino acid sequence of SEQID NO: 15.

In one embodiment, an antibody that specifically binds to OX40 comprisesa heavy chain variable region comprising the amino acid sequence of SEQID NO: 16; and a light chain variable region comprising the amino acidsequence of SEQ ID NO: 15.

In one embodiment, the antibody comprises a heavy chain comprising theamino acid sequence of SEQ ID NO: 21; and a light chain comprising theamino acid sequence of SEQ ID NO: 20. In one embodiment, the antibodycomprises a heavy chain comprising the amino acid sequence of SEQ ID NO:60; and a light chain comprising the amino acid sequence of SEQ ID NO:20.

In one embodiment, the antibody comprises a heavy chain comprising theamino acid sequence of SEQ ID NO: 23; and a light chain comprising theamino acid sequence of SEQ ID NO: 20. In one embodiment, the antibodycomprises a heavy chain comprising the amino acid sequence of SEQ ID NO:61; and a light chain comprising the amino acid sequence of SEQ ID NO:20.

In one embodiment, the antibody comprises a heavy chain comprising theamino acid sequence of SEQ ID NO: 51 or 52; and a light chain comprisingthe amino acid sequence of SEQ ID NO: 20. In one embodiment, theantibody comprises a heavy chain comprising the amino acid sequence ofSEQ ID NO: 62 or 63; and a light chain comprising the amino acidsequence of SEQ ID NO: 20.

In one embodiment, the antibody comprises heavy and/or light chainconstant regions. In one embodiment, the heavy chain constant region isselected from the group consisting of human immunoglobulins IgG₁, IgG₂,IgG₃, IgG₄, IgA₁, and IgA₂. In one embodiment, the IgG₁ isnon-fucosylated IgG₁. In one embodiment, the amino acid sequence of IgG₁comprises a N297A mutation. In one embodiment, the amino acid sequenceof IgG₁ comprises a mutation selected from the group consisting ofD265A, P329A, and a combination thereof. In one embodiment, the aminoacid sequence of IgG₁ comprises a N297Q mutation. In one embodiment, theamino acid sequence of IgG₄ comprises a S228P mutation. In oneembodiment, the amino acid sequence of IgG₂ comprises a C127S mutation.In one embodiment, the heavy chain constant region comprises an aminoacid sequence selected from the group consisting of SEQ ID NOs: 32-37,53-54, and 64-71. In one embodiment, the light chain constant region isselected from the group consisting of human immunoglobulins IgGκ andIgGλ.

In one embodiment, the antibody is a human antibody.

In one embodiment, an antibody that specifically binds to OX40 binds tothe same epitope of human OX40 as an antibody comprising a VH CDR1comprising the amino acid sequence of GSAMH (SEQ ID NO: 4); a VH CDR2comprising the amino acid sequence of RIRSKANSYATAYAASVKG (SEQ ID NO:5); a VH CDR3 comprising the amino acid sequence of GIYDSSGYDY (SEQ IDNO: 6); a VL CDR1 comprising the amino acid sequence of RSSQSLLHSNGYNYLD(SEQ ID NO: 1); a VL CDR2 comprising the amino acid sequence of LGSNRAS(SEQ ID NO: 2); and a VL CDR3 comprising the amino acid sequence ofMQALQTPLT (SEQ ID NO: 3). In one embodiment, an antibody thatspecifically binds to OX40 binds to the same epitope of human OX40 as anantibody comprising a VH CDR1 comprising the amino acid sequence ofGFTFSGSA (SEQ ID NO: 47); a VH CDR2 comprising the amino acid sequenceof IRSKANSYAT (SEQ ID NO: 48); a VH CDR3 comprising the amino acidsequence of TSGIYDSSGYDY (SEQ ID NO: 49); a VL CDR1 comprising the aminoacid sequence of QSLLHSNGYNY (SEQ ID NO: 44); a VL CDR2 comprising theamino acid sequence of LGS (SEQ ID NO: 45); and a VL CDR3 comprising theamino acid sequence of MQALQTPLT (SEQ ID NO: 46). In one embodiment, anantibody that specifically binds to OX40 binds to the same epitope ofhuman OX40 as an antibody comprising a heavy chain variable regioncomprising the amino acid sequence of SEQ ID NO: 16; and a light chainvariable region comprising the amino acid sequence of SEQ ID NO: 15.

In one embodiment, the antibody is agonistic. In one embodiment, theantibody activates, enhances, or induces an activity of human OX40. Inone embodiment, the antibody induces CD4+ T cell proliferation. In oneembodiment, the CD4+ T cell proliferation is a substantially increasingfunction of the concentration of the antibody. In one embodiment, theCD4+ T cell proliferation shows a sigmoidal dose response curve. In oneembodiment, the antibody induces production of IL-2, TNFα, IFNγ, IL-4,IL-10, IL-13, or a combination thereof by anti-CD3-stimulated T cells.In one embodiment, the antibody induces production of TNFα, TNFβ, IFNγ,GM-CSF, IL-2, IL-4, IL-10, IL-13, or a combination thereof byanti-CD3-stimulated peripheral blood mononuclear cells (PBMCs). In oneembodiment, the antibody induces production of TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13 by anti-CD3-stimulated PBMCs, wherein theproduction of TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13 is asubstantially increasing function of the concentration of the antibody.In one embodiment, the antibody induces production of TNFα, TNFβ, IFNγ,GM-CSF, IL-2, IL-10, or IL-13 by anti-CD3-stimulated PBMCs, wherein theproduction of TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13 shows asigmoidal dose response curve. In one embodiment, the antibody inducesproduction of IL-2 by SEA-stimulated T cells and suppresses productionof IL-10 by SEA-stimulated T cells. In one embodiment, the antibodyinduces IL-2 production by SEA-stimulated peripheral blood mononuclearcells (PBMCs) and suppresses IL-2 production by SEA-stimulated PBMCs. Inone embodiment, the antibody induces IL-2 production by SEA-stimulatedPBMCs, wherein the IL-2 production is a substantially increasingfunction of the concentration of the antibody. In one embodiment, theantibody the antibody induces IL-2 production by SEA-stimulated PBMCs,wherein the IL-2 production shows a sigmoidal dose response curve.

In one embodiment, the antibody relieves suppression of T effector cellsby T regulatory cells.

In one embodiment, the antibody induces IL-2 production by a co-cultureof T effector cells and T regulatory cells and suppresses IL-10production by a co-culture of T effector cells and T regulatory cells.

In one embodiment, an antibody that specifically binds to OX40 comprisesa VH CDR1 comprising the amino acid sequence of GSAMH (SEQ ID NO: 4); aVH CDR2 comprising the amino acid sequence of RIRSKANSYATAYAASVKG (SEQID NO: 5); a VH CDR3 comprising the amino acid sequence of GIYDSSGYDY(SEQ ID NO: 6); a VL CDR1 comprising the amino acid sequence ofRSSQSLLHSNGYNYLD (SEQ ID NO: 1); a VL CDR2 comprising the amino acidsequence of LGSNRAS (SEQ ID NO: 2); and a VL CDR3 comprising the aminoacid sequence of MQALQTPLT (SEQ ID NO: 3), wherein the antibody, incombination with Staphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml),induces IL-2 production in, e.g., PBMCs upon stimulation for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity, as measured by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery), wherein the IL-2 production is a substantiallyincreasing function of antibody concentrations between, e.g., 0.032μg/ml and 20 μg/ml, 0.16 μg/ml and 20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4μg/ml and 20 μg/ml, 0.032 μg/ml and 4 μg/ml, 0.16 μg/ml and 4 μg/ml, or0.8 μg/ml and 4 μg/ml. The IL-2 production can be assessed in, e.g., anassay comprising the following steps: (a) culturing the PBMCs (e.g., 10⁵cells in a well) in the absence or presence of varying concentrations(e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and 0.000256 μg/ml) ofthe antibody and, e.g., 100 ng/ml of SEA for, e.g., 5 days at, e.g., 37°C., 5% CO₂, and 97% humidity; and (b) collecting clarified supernatantand measuring the titer of IL-2 by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery).In one embodiment, an antibody that specifically binds to OX40 comprisesa VH CDR1 comprising the amino acid sequence of GSAMH (SEQ ID NO: 4); aVH CDR2 comprising the amino acid sequence of RIRSKANSYATAYAASVKG (SEQID NO: 5); a VH CDR3 comprising the amino acid sequence of GIYDSSGYDY(SEQ ID NO: 6); a VL CDR1 comprising the amino acid sequence ofRSSQSLLHSNGYNYLD (SEQ ID NO: 1); a VL CDR2 comprising the amino acidsequence of LGSNRAS (SEQ ID NO: 2); and a VL CDR3 comprising the aminoacid sequence of MQALQTPLT (SEQ ID NO: 3), wherein the antibody, incombination with Staphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml),induces IL-2 production in, e.g., PBMCs upon stimulation for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity, as measured by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery), wherein the IL-2 production shows a sigmoidaldose response curve when the anti-OX40 antibody concentration isbetween, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and 20 μg/ml, 0.8μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and 4 μg/ml, 0.16μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessed in, e.g., anassay comprising the following steps: (a) culturing the PBMCs (e.g., 10⁵cells in a well) in the absence or presence of varying concentrations(e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and 0.000256 μg/ml) ofthe antibody and, e.g., 100 ng/ml of SEA for, e.g., 5 days at, e.g., 37°C., 5% CO₂, and 97% humidity; and (b) collecting clarified supernatantand measuring the titer of IL-2 by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery).

In one embodiment, an antibody that specifically binds to OX40 comprisesa VH CDR1 comprising the amino acid sequence of GSAMH (SEQ ID NO: 4); aVH CDR2 comprising the amino acid sequence of RIRSKANSYATAYAASVKG (SEQID NO: 5); a VH CDR3 comprising the amino acid sequence of GIYDSSGYDY(SEQ ID NO: 6); a VL CDR1 comprising the amino acid sequence ofRSSQSLLHSNGYNYLD (SEQ ID NO: 1); a VL CDR2 comprising the amino acidsequence of LGSNRAS (SEQ ID NO: 2); and a VL CDR3 comprising the aminoacid sequence of MQALQTPLT (SEQ ID NO: 3), wherein the antibody, incombination with Staphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml),induces IL-2 production in, e.g., PBMCs upon stimulation for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity, as measured by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery), wherein the IL-2 production is greater in thepresence of 4 μg/ml of the antibody than in the presence of 0.032 μg/mlof the antibody. The IL-2 production can be assessed in, e.g., an assaycomprising the following steps: (a) culturing the PBMCs (e.g., 10⁵ cellsin a well) in the absence or presence of varying concentrations (e.g.,20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of theantibody and, e.g., 100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C.,5% CO₂, and 97% humidity; and (b) collecting clarified supernatant andmeasuring the titer of IL-2 by, e.g., electrochemiluminescence, e.g.,Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery).

In one embodiment, an antibody that specifically binds to OX40 comprisesa VH CDR1 comprising the amino acid sequence of GSAMH (SEQ ID NO: 4); aVH CDR2 comprising the amino acid sequence of RIRSKANSYATAYAASVKG (SEQID NO: 5); a VH CDR3 comprising the amino acid sequence of GIYDSSGYDY(SEQ ID NO: 6); a VL CDR1 comprising the amino acid sequence ofRSSQSLLHSNGYNYLD (SEQ ID NO: 1); a VL CDR2 comprising the amino acidsequence of LGSNRAS (SEQ ID NO: 2); and a VL CDR3 comprising the aminoacid sequence of MQALQTPLT (SEQ ID NO: 3), wherein the antibody whenplate-bound, in combination with a plate-bound anti-CD3 antibody (e.g.,0.8 μg/ml), induces production of one or more cytokines, e.g., TNFα,TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCs or T cellsupon stimulation for, e.g., 4 days at, e.g., 37° C. and 5% CO₂, asmeasured by, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plextissue culture kit (Meso Scale Discovery) or non-human primate (NHP)V-Plex assay kit (Meso Scale Discovery), wherein the production of oneor more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, is a substantially increasing function of the concentrations ofthe antibody between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery). In one embodiment, an antibody thatspecifically binds to OX40 comprises a VH CDR1 comprising the amino acidsequence of GSAMH (SEQ ID NO: 4); a VH CDR2 comprising the amino acidsequence of RIRSKANSYATAYAASVKG (SEQ ID NO: 5); a VH CDR3 comprising theamino acid sequence of GIYDSSGYDY (SEQ ID NO: 6); a VL CDR1 comprisingthe amino acid sequence of RSSQSLLHSNGYNYLD (SEQ ID NO: 1); a VL CDR2comprising the amino acid sequence of LGSNRAS (SEQ ID NO: 2); and a VLCDR3 comprising the amino acid sequence of MQALQTPLT (SEQ ID NO: 3),wherein the antibody when plate-bound, in combination with a plate-boundanti-CD3 antibody (e.g., 0.8 μg/ml), induces production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in,e.g., PBMCs or T cells upon stimulation for, e.g., 4 days at, e.g., 37°C. and 5% CO₂, as measured by, e.g., electrochemiluminescence, e.g.,Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery), whereinthe production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13, shows a sigmoidal dose response curve when theanti-OX40 antibody concentration is between, e.g., 0.7 μg/ml and 50μg/ml, 1.6 μg/ml and 50 μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and50 μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs in the presence of a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml) and varying concentrations (e.g., 0, 0.3, 1,3, 6, 12, 25, and 50 μm/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50μg/ml) of the plate-bound antibody for, e.g., 4 days at, e.g., 37° C.and 5% CO₂; and (b) collecting supernatant and measuring the productionof one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10,or IL-13, by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery).

In one embodiment, an antibody that specifically binds to OX40 comprisesa VH CDR1 comprising the amino acid sequence of GSAMH (SEQ ID NO: 4); aVH CDR2 comprising the amino acid sequence of RIRSKANSYATAYAASVKG (SEQID NO: 5); a VH CDR3 comprising the amino acid sequence of GIYDSSGYDY(SEQ ID NO: 6); a VL CDR1 comprising the amino acid sequence ofRSSQSLLHSNGYNYLD (SEQ ID NO: 1); a VL CDR2 comprising the amino acidsequence of LGSNRAS (SEQ ID NO: 2); and a VL CDR3 comprising the aminoacid sequence of MQALQTPLT (SEQ ID NO: 3), wherein the antibodyincreases CD4+ T cell proliferation, wherein the CD4+ T cellproliferation is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.2 μg/ml and 20 μg/ml, or2 μg/ml and 20 μg/ml, as assessed in, e.g., an assay comprising thefollowing steps: (a) labeling, e.g., enriched CD4+ T cells with, e.g.,10 μM carboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In one embodiment, an antibody that specificallybinds to OX40 comprises a VH CDR1 comprising the amino acid sequence ofGSAMH (SEQ ID NO: 4); a VH CDR2 comprising the amino acid sequence ofRIRSKANSYATAYAASVKG (SEQ ID NO: 5); a VH CDR3 comprising the amino acidsequence of GIYDSSGYDY (SEQ ID NO: 6); a VL CDR1 comprising the aminoacid sequence of RSSQSLLHSNGYNYLD (SEQ ID NO: 1); a VL CDR2 comprisingthe amino acid sequence of LGSNRAS (SEQ ID NO: 2); and a VL CDR3comprising the amino acid sequence of MQALQTPLT (SEQ ID NO: 3), whereinthe antibody increases CD4+ T cell proliferation, wherein the CD4+ Tcell proliferation shows a sigmoidal dose response curve when theanti-OX40 antibody concentration is between, e.g., 0.2 μg/ml and 20μg/ml, or 2 μg/ml and 20 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In one embodiment, an antibody that specifically binds to OX40 comprisesa VH CDR1 comprising the amino acid sequence of GSAMH (SEQ ID NO: 4); aVH CDR2 comprising the amino acid sequence of RIRSKANSYATAYAASVKG (SEQID NO: 5); a VH CDR3 comprising the amino acid sequence of GIYDSSGYDY(SEQ ID NO: 6); a VL CDR1 comprising the amino acid sequence ofRSSQSLLHSNGYNYLD (SEQ ID NO: 1); a VL CDR2 comprising the amino acidsequence of LGSNRAS (SEQ ID NO: 2); and a VL CDR3 comprising the aminoacid sequence of MQALQTPLT (SEQ ID NO: 3), wherein the antibody resultsin a greater increase in CD4+ T cell proliferation when the antibody ispresent at a concentration of 20 μg/ml than at a concentration of 2μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 70%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 70% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is a substantially increasing function of antibodyconcentrations between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. The IL-2production can be assessed in, e.g., an assay comprising the followingsteps: (a) culturing the PBMCs (e.g., 10⁵ cells in a well) in theabsence or presence of varying concentrations (e.g., 20, 4, 0.8, 0.16,0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g.,100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 70% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 70%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA) (e.g.,100 ng/ml), induces IL-2 production in, e.g., PBMCs upon stimulationfor, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97% humidity, asmeasured by, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plextissue culture kit (Meso Scale Discovery), wherein the IL-2 productionshows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs (e.g., 10⁵ cells in a well) in the absence or presence of varyingconcentrations (e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and0.000256 μg/ml) of the antibody and, e.g., 100 ng/ml of SEA for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity; and (b) collectingclarified supernatant and measuring the titer of IL-2 by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 70%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 70% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is greater in the presence of 4 μg/ml of the antibodythan in the presence of 0.032 μg/ml of the antibody. The IL-2 productioncan be assessed in, e.g., an assay comprising the following steps: (a)culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 75%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 75% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is a substantially increasing function of antibodyconcentrations between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. The IL-2production can be assessed in, e.g., an assay comprising the followingsteps: (a) culturing the PBMCs (e.g., 10⁵ cells in a well) in theabsence or presence of varying concentrations (e.g., 20, 4, 0.8, 0.16,0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g.,100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 75% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 75%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA) (e.g.,100 ng/ml), induces IL-2 production in, e.g., PBMCs upon stimulationfor, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97% humidity, asmeasured by, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plextissue culture kit (Meso Scale Discovery), wherein the IL-2 productionshows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs (e.g., 10⁵ cells in a well) in the absence or presence of varyingconcentrations (e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and0.000256 μg/ml) of the antibody and, e.g., 100 ng/ml of SEA for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity; and (b) collectingclarified supernatant and measuring the titer of IL-2 by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 75%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 75% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is greater in the presence of 4 μg/ml of the antibodythan in the presence of 0.032 μg/ml of the antibody. The IL-2 productioncan be assessed in, e.g., an assay comprising the following steps: (a)culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 80%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 80% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is a substantially increasing function of antibodyconcentrations between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. The IL-2production can be assessed in, e.g., an assay comprising the followingsteps: (a) culturing the PBMCs (e.g., 10⁵ cells in a well) in theabsence or presence of varying concentrations (e.g., 20, 4, 0.8, 0.16,0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g.,100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 80% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 80%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA) (e.g.,100 ng/ml), induces IL-2 production in, e.g., PBMCs upon stimulationfor, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97% humidity, asmeasured by, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plextissue culture kit (Meso Scale Discovery), wherein the IL-2 productionshows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs (e.g., 10⁵ cells in a well) in the absence or presence of varyingconcentrations (e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and0.000256 μg/ml) of the antibody and, e.g., 100 ng/ml of SEA for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity; and (b) collectingclarified supernatant and measuring the titer of IL-2 by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 80%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 80% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is greater in the presence of 4 μg/ml of the antibodythan in the presence of 0.032 μg/ml of the antibody. The IL-2 productioncan be assessed in, e.g., an assay comprising the following steps: (a)culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 85%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 85% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is a substantially increasing function of antibodyconcentrations between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. The IL-2production can be assessed in, e.g., an assay comprising the followingsteps: (a) culturing the PBMCs (e.g., 10⁵ cells in a well) in theabsence or presence of varying concentrations (e.g., 20, 4, 0.8, 0.16,0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g.,100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 85% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 85%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA) (e.g.,100 ng/ml), induces IL-2 production in, e.g., PBMCs upon stimulationfor, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97% humidity, asmeasured by, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plextissue culture kit (Meso Scale Discovery), wherein the IL-2 productionshows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs (e.g., 10⁵ cells in a well) in the absence or presence of varyingconcentrations (e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and0.000256 μg/ml) of the antibody and, e.g., 100 ng/ml of SEA for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity; and (b) collectingclarified supernatant and measuring the titer of IL-2 by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 85%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 85% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is greater in the presence of 4 μg/ml of the antibodythan in the presence of 0.032 μg/ml of the antibody. The IL-2 productioncan be assessed in, e.g., an assay comprising the following steps: (a)culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 90%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 90% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is a substantially increasing function of antibodyconcentrations between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. The IL-2production can be assessed in, e.g., an assay comprising the followingsteps: (a) culturing the PBMCs (e.g., 10⁵ cells in a well) in theabsence or presence of varying concentrations (e.g., 20, 4, 0.8, 0.16,0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g.,100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 90% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 90%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA) (e.g.,100 ng/ml), induces IL-2 production in, e.g., PBMCs upon stimulationfor, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97% humidity, asmeasured by, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plextissue culture kit (Meso Scale Discovery), wherein the IL-2 productionshows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs (e.g., 10⁵ cells in a well) in the absence or presence of varyingconcentrations (e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and0.000256 μg/ml) of the antibody and, e.g., 100 ng/ml of SEA for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity; and (b) collectingclarified supernatant and measuring the titer of IL-2 by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 90%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 90% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is greater in the presence of 4 μg/ml of the antibodythan in the presence of 0.032 μg/ml of the antibody. The IL-2 productioncan be assessed in, e.g., an assay comprising the following steps: (a)culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 95%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 95% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is a substantially increasing function of antibodyconcentrations between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. The IL-2production can be assessed in, e.g., an assay comprising the followingsteps: (a) culturing the PBMCs (e.g., 10⁵ cells in a well) in theabsence or presence of varying concentrations (e.g., 20, 4, 0.8, 0.16,0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g.,100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 95% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 95%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA) (e.g.,100 ng/ml), induces IL-2 production in, e.g., PBMCs upon stimulationfor, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97% humidity, asmeasured by, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plextissue culture kit (Meso Scale Discovery), wherein the IL-2 productionshows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs (e.g., 10⁵ cells in a well) in the absence or presence of varyingconcentrations (e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and0.000256 μg/ml) of the antibody and, e.g., 100 ng/ml of SEA for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity; and (b) collectingclarified supernatant and measuring the titer of IL-2 by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 95%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 95% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is greater in the presence of 4 μg/ml of the antibodythan in the presence of 0.032 μg/ml of the antibody. The IL-2 productioncan be assessed in, e.g., an assay comprising the following steps: (a)culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 98%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 98% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is a substantially increasing function of antibodyconcentrations between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. The IL-2production can be assessed in, e.g., an assay comprising the followingsteps: (a) culturing the PBMCs (e.g., 10⁵ cells in a well) in theabsence or presence of varying concentrations (e.g., 20, 4, 0.8, 0.16,0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g.,100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 98% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 98%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA) (e.g.,100 ng/ml), induces IL-2 production in, e.g., PBMCs upon stimulationfor, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97% humidity, asmeasured by, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plextissue culture kit (Meso Scale Discovery), wherein the IL-2 productionshows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs (e.g., 10⁵ cells in a well) in the absence or presence of varyingconcentrations (e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and0.000256 μg/ml) of the antibody and, e.g., 100 ng/ml of SEA for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity; and (b) collectingclarified supernatant and measuring the titer of IL-2 by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 98%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 98% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody, in combination with Staphylococcus EnterotoxinA (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g., PBMCs uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, as measured by, e.g., electrochemiluminescence, e.g., HumanTH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), wherein theIL-2 production is greater in the presence of 4 μg/ml of the antibodythan in the presence of 0.032 μg/ml of the antibody. The IL-2 productioncan be assessed in, e.g., an assay comprising the following steps: (a)culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 70%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 70% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody when plate-bound, in combination with aplate-bound anti-CD3 antibody (e.g., 0.8 μg/ml), induces production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, in, e.g., PBMCs or T cells upon stimulation for, e.g., 4 days at,e.g., 37° C. and 5% CO₂, as measured by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery), whereinthe production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13, is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.7 μg/ml and 50 μg/ml,1.6 μg/ml and 50 μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs in the presence of a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml) and varying concentrations (e.g., 0, 0.3, 1,3, 6, 12, 25, and 50 μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50μg/ml) of the plate-bound antibody for, e.g., 4 days at, e.g., 37° C.and 5% CO₂; and (b) collecting supernatant and measuring the productionof one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10,or IL-13, by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 70% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 70%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody hen plate-bound, in combination with a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml), induces production of one or more cytokines,e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCsor T cells upon stimulation for, e.g., 4 days at, e.g., 37° C. and 5%CO₂, as measured by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery), wherein the production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, shows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 75%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 75% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody when plate-bound, in combination with aplate-bound anti-CD3 antibody (e.g., 0.8 μg/ml), induces production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, in, e.g., PBMCs or T cells upon stimulation for, e.g., 4 days at,e.g., 37° C. and 5% CO₂, as measured by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery), whereinthe production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13, is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.7 μg/ml and 50 μg/ml,1.6 μg/ml and 50 μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs in the presence of a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml) and varying concentrations (e.g., 0, 0.3, 1,3, 6, 12, 25, and 50 μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50μg/ml) of the plate-bound antibody for, e.g., 4 days at, e.g., 37° C.and 5% CO₂; and (b) collecting supernatant and measuring the productionof one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10,or IL-13, by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 75% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 75%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody hen plate-bound, in combination with a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml), induces production of one or more cytokines,e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCsor T cells upon stimulation for, e.g., 4 days at, e.g., 37° C. and 5%CO₂, as measured by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery), wherein the production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, shows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 80%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 80% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody when plate-bound, in combination with aplate-bound anti-CD3 antibody (e.g., 0.8 μg/ml), induces production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, in, e.g., PBMCs or T cells upon stimulation for, e.g., 4 days at,e.g., 37° C. and 5% CO₂, as measured by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery), whereinthe production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13, is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.7 μg/ml and 50 μg/ml,1.6 μg/ml and 50 μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs in the presence of a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml) and varying concentrations (e.g., 0, 0.3, 1,3, 6, 12, 25, and 50 μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50μg/ml) of the plate-bound antibody for, e.g., 4 days at, e.g., 37° C.and 5% CO₂; and (b) collecting supernatant and measuring the productionof one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10,or IL-13, by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 80% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 80%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody hen plate-bound, in combination with a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml), induces production of one or more cytokines,e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCsor T cells upon stimulation for, e.g., 4 days at, e.g., 37° C. and 5%CO₂, as measured by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery), wherein the production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, shows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 85%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 85% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody when plate-bound, in combination with aplate-bound anti-CD3 antibody (e.g., 0.8 μg/ml), induces production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, in, e.g., PBMCs or T cells upon stimulation for, e.g., 4 days at,e.g., 37° C. and 5% CO₂, as measured by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery), whereinthe production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13, is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.7 μg/ml and 50 μg/ml,1.6 μg/ml and 50 μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs in the presence of a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml) and varying concentrations (e.g., 0, 0.3, 1,3, 6, 12, 25, and 50 μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50μg/ml) of the plate-bound antibody for, e.g., 4 days at, e.g., 37° C.and 5% CO₂; and (b) collecting supernatant and measuring the productionof one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10,or IL-13, by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 85% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 85%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody hen plate-bound, in combination with a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml), induces production of one or more cytokines,e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCsor T cells upon stimulation for, e.g., 4 days at, e.g., 37° C. and 5%CO₂, as measured by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery), wherein the production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, shows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 90%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 90% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody when plate-bound, in combination with aplate-bound anti-CD3 antibody (e.g., 0.8 μg/ml), induces production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, in, e.g., PBMCs or T cells upon stimulation for, e.g., 4 days at,e.g., 37° C. and 5% CO₂, as measured by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery), whereinthe production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13, is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.7 μg/ml and 50 μg/ml,1.6 μg/ml and 50 μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs in the presence of a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml) and varying concentrations (e.g., 0, 0.3, 1,3, 6, 12, 25, and 50 μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50μg/ml) of the plate-bound antibody for, e.g., 4 days at, e.g., 37° C.and 5% CO₂; and (b) collecting supernatant and measuring the productionof one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10,or IL-13, by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 90% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 90%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody hen plate-bound, in combination with a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml), induces production of one or more cytokines,e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCsor T cells upon stimulation for, e.g., 4 days at, e.g., 37° C. and 5%CO₂, as measured by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery), wherein the production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, shows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 95%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 95% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody when plate-bound, in combination with aplate-bound anti-CD3 antibody (e.g., 0.8 μg/ml), induces production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, in, e.g., PBMCs or T cells upon stimulation for, e.g., 4 days at,e.g., 37° C. and 5% CO₂, as measured by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery), whereinthe production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13, is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.7 μg/ml and 50 μg/ml,1.6 μg/ml and 50 μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs in the presence of a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml) and varying concentrations (e.g., 0, 0.3, 1,3, 6, 12, 25, and 50 μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50μg/ml) of the plate-bound antibody for, e.g., 4 days at, e.g., 37° C.and 5% CO₂; and (b) collecting supernatant and measuring the productionof one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10,or IL-13, by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 95% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 95%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody hen plate-bound, in combination with a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml), induces production of one or more cytokines,e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCsor T cells upon stimulation for, e.g., 4 days at, e.g., 37° C. and 5%CO₂, as measured by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery), wherein the production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, shows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 98%identity to the amino acid sequence of SEQ ID NO: 15 and a VH domainhaving at least 98% identity to the amino acid sequence of SEQ ID NO:16, wherein the antibody when plate-bound, in combination with aplate-bound anti-CD3 antibody (e.g., 0.8 μg/ml), induces production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, in, e.g., PBMCs or T cells upon stimulation for, e.g., 4 days at,e.g., 37° C. and 5% CO₂, as measured by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery), whereinthe production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13, is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.7 μg/ml and 50 μg/ml,1.6 μg/ml and 50 μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs in the presence of a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml) and varying concentrations (e.g., 0, 0.3, 1,3, 6, 12, 25, and 50 μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50μg/ml) of the plate-bound antibody for, e.g., 4 days at, e.g., 37° C.and 5% CO₂; and (b) collecting supernatant and measuring the productionof one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10,or IL-13, by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery). In one embodiment, anantibody comprises a VL domain having at least 98% identity to the aminoacid sequence of SEQ ID NO: 15 and a VH domain having at least 98%identity to the amino acid sequence of SEQ ID NO: 16, wherein theantibody hen plate-bound, in combination with a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml), induces production of one or more cytokines,e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCsor T cells upon stimulation for, e.g., 4 days at, e.g., 37° C. and 5%CO₂, as measured by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery), wherein the production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, shows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

In one embodiment, an antibody comprises a VL domain having at least 70%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 70% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody increases CD4+ T cell proliferation, wherein theCD4+ T cell proliferation is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.2 μg/ml and 20 μg/ml, or2 μg/ml and 20 μg/ml, as assessed in, e.g., an assay comprising thefollowing steps: (a) labeling, e.g., enriched CD4+ T cells with, e.g.,10 μM carboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In one embodiment, an antibody comprises a VL domainhaving at least 70% identity to the amino acid sequence SEQ ID NO: 15and a VH domain having at least 70% identity to the amino acid sequenceof SEQ ID NO: 16, wherein the antibody increases CD4+ T cellproliferation, wherein the CD4+ T cell proliferation shows a sigmoidaldose response curve when the anti-OX40 antibody concentration isbetween, e.g., 0.2 μg/ml and 20 μg/ml, or 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 70%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 70% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody results in a greater increase in CD4+ T cellproliferation when the antibody is present at a concentration of 20μg/ml than at a concentration of 2 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 75%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 75% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody increases CD4+ T cell proliferation, wherein theCD4+ T cell proliferation is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.2 μg/ml and 20 μg/ml, or2 μg/ml and 20 μg/ml, as assessed in, e.g., an assay comprising thefollowing steps: (a) labeling, e.g., enriched CD4+ T cells with, e.g.,10 μM carboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In one embodiment, an antibody comprises a VL domainhaving at least 75% identity to the amino acid sequence SEQ ID NO: 15and a VH domain having at least 75% identity to the amino acid sequenceof SEQ ID NO: 16, wherein the antibody increases CD4+ T cellproliferation, wherein the CD4+ T cell proliferation shows a sigmoidaldose response curve when the anti-OX40 antibody concentration isbetween, e.g., 0.2 μg/ml and 20 μg/ml, or 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 75%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 75% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody results in a greater increase in CD4+ T cellproliferation when the antibody is present at a concentration of 20μg/ml than at a concentration of 2 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 80%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 80% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody increases CD4+ T cell proliferation, wherein theCD4+ T cell proliferation is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.2 μg/ml and 20 μg/ml, or2 μg/ml and 20 μg/ml, as assessed in, e.g., an assay comprising thefollowing steps: (a) labeling, e.g., enriched CD4+ T cells with, e.g.,10 μM carboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In one embodiment, an antibody comprises a VL domainhaving at least 80% identity to the amino acid sequence SEQ ID NO: 15and a VH domain having at least 80% identity to the amino acid sequenceof SEQ ID NO: 16, wherein the antibody increases CD4+ T cellproliferation, wherein the CD4+ T cell proliferation shows a sigmoidaldose response curve when the anti-OX40 antibody concentration isbetween, e.g., 0.2 μg/ml and 20 μg/ml, or 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 80%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 80% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody results in a greater increase in CD4+ T cellproliferation when the antibody is present at a concentration of 20μg/ml than at a concentration of 2 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 85%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 85% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody increases CD4+ T cell proliferation, wherein theCD4+ T cell proliferation is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.2 μg/ml and 20 μg/ml, or2 μg/ml and 20 μg/ml, as assessed in, e.g., an assay comprising thefollowing steps: (a) labeling, e.g., enriched CD4+ T cells with, e.g.,10 μM carboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In one embodiment, an antibody comprises a VL domainhaving at least 85% identity to the amino acid sequence SEQ ID NO: 15and a VH domain having at least 85% identity to the amino acid sequenceof SEQ ID NO: 16, wherein the antibody increases CD4+ T cellproliferation, wherein the CD4+ T cell proliferation shows a sigmoidaldose response curve when the anti-OX40 antibody concentration isbetween, e.g., 0.2 μg/ml and 20 μg/ml, or 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 85%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 85% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody results in a greater increase in CD4+ T cellproliferation when the antibody is present at a concentration of 20μg/ml than at a concentration of 2 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 90%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 90% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody increases CD4+ T cell proliferation, wherein theCD4+ T cell proliferation is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.2 μg/ml and 20 μg/ml, or2 μg/ml and 20 μg/ml, as assessed in, e.g., an assay comprising thefollowing steps: (a) labeling, e.g., enriched CD4+ T cells with, e.g.,10 μM carboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In one embodiment, an antibody comprises a VL domainhaving at least 90% identity to the amino acid sequence SEQ ID NO: 15and a VH domain having at least 90% identity to the amino acid sequenceof SEQ ID NO: 16, wherein the antibody increases CD4+ T cellproliferation, wherein the CD4+ T cell proliferation shows a sigmoidaldose response curve when the anti-OX40 antibody concentration isbetween, e.g., 0.2 μg/ml and 20 μg/ml, or 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 90%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 90% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody results in a greater increase in CD4+ T cellproliferation when the antibody is present at a concentration of 20μg/ml than at a concentration of 2 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 95%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 95% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody increases CD4+ T cell proliferation, wherein theCD4+ T cell proliferation is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.2 μg/ml and 20 μg/ml, or2 μg/ml and 20 μg/ml, as assessed in, e.g., an assay comprising thefollowing steps: (a) labeling, e.g., enriched CD4+ T cells with, e.g.,10 μM carboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In one embodiment, an antibody comprises a VL domainhaving at least 95% identity to the amino acid sequence SEQ ID NO: 15and a VH domain having at least 95% identity to the amino acid sequenceof SEQ ID NO: 16, wherein the antibody increases CD4+ T cellproliferation, wherein the CD4+ T cell proliferation shows a sigmoidaldose response curve when the anti-OX40 antibody concentration isbetween, e.g., 0.2 μg/ml and 20 μg/ml, or 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 95%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 95% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody results in a greater increase in CD4+ T cellproliferation when the antibody is present at a concentration of 20μg/ml than at a concentration of 2 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 98%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 98% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody increases CD4+ T cell proliferation, wherein theCD4+ T cell proliferation is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.2 μg/ml and 20 μg/ml, or2 μg/ml and 20 μg/ml, as assessed in, e.g., an assay comprising thefollowing steps: (a) labeling, e.g., enriched CD4+ T cells with, e.g.,10 μM carboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In one embodiment, an antibody comprises a VL domainhaving at least 98% identity to the amino acid sequence SEQ ID NO: 15and a VH domain having at least 98% identity to the amino acid sequenceof SEQ ID NO: 16, wherein the antibody increases CD4+ T cellproliferation, wherein the CD4+ T cell proliferation shows a sigmoidaldose response curve when the anti-OX40 antibody concentration isbetween, e.g., 0.2 μg/ml and 20 μg/ml, or 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In one embodiment, an antibody comprises a VL domain having at least 98%identity to the amino acid sequence SEQ ID NO: 15 and a VH domain havingat least 98% identity to the amino acid sequence of SEQ ID NO: 16,wherein the antibody results in a greater increase in CD4+ T cellproliferation when the antibody is present at a concentration of 20μg/ml than at a concentration of 2 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂, and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In one embodiment, an antibody comprises a human immunoglobulin IgG₁heavy chain constant region, wherein the amino acid sequence of the IgG₁heavy chain constant region comprises a mutation selected from the groupconsisting of N297A, N297Q, D265A, and a combination thereof. In oneembodiment, the antibody comprises an IgG₁ heavy chain constant region,wherein the amino acid sequence of the IgG₁ heavy chain constant regioncomprises a mutation selected from the group consisting of D265A, P329A,and a combination thereof.

In one embodiment, an antibody that specifically binds to human OX40 isan antibody wherein the binding between the antibody and a variant OX40is substantially weakened relative to the binding between the antibodyand a human OX40 sequence of SEQ ID NO:55, and wherein the variant OX40comprises the sequence of SEQ ID NO: 55 except for an amino acidmutation selected from the group consisting of: N60A, R62A, R80A, L88A,P93A, P99A, P115A, and a combination thereof.

In one embodiment, an antibody that specifically binds to human OX40 isan antibody wherein the binding between the antibody and a variant OX40is substantially weakened relative to the binding between the antibodyand a human OX40 sequence of SEQ ID NO:55, and wherein the variant OX40comprises the sequence of SEQ ID NO: 55 except for the amino acidmutations W58A, N60A, R62A, R80A, L88A, P93A, P99A, and P115A.

In one embodiment, an antibody that specifically binds to human OX40 isan antibody that exhibits, as compared to binding to a human OX40sequence of SEQ ID NO: 55, reduced or absent binding to a proteinidentical to SEQ ID NO: 55 except for the presence of an amino acidmutation selected from the group consisting of: N60A, R62A, R80A, L88A,P93A, P99A, P115A, and a combination thereof.

In one embodiment, an antibody that specifically binds to human OX40. Anisolated antibody that specifically binds to human OX40, wherein theantibody exhibits, as compared to binding to a human OX40 sequence ofSEQ ID NO: 55, reduced or absent binding to a protein identical to SEQID NO: 55 except for the presence of the amino acid mutations W58A,N60A, R62A, R80A, L88A, P93A, P99A, and P115A.

In one embodiment, an antibody that specifically binds to human OX40 isan antibody that specifically binds to an epitope of a human OX40sequence comprising a residue of SEQ ID NO: 55 selected from the groupconsisting of: 60, 62, 80, 88, 93, 99, 115, and a combination thereof.

In one embodiment, an antibody that specifically binds to human OX40 isan antibody that specifically binds to an epitope of a human OX40sequence comprising residues 58, 60, 62, 80, 88, 93, 99, and 115 of SEQID NO: 55.

In one embodiment, an antibody that specifically binds to human OX40 isan antibody that specifically binds to at least one residue of SEQ IDNO: 55 selected from the group consisting of: 60, 62, 80, 88, 93, 99,115, and a combination thereof.

In one embodiment, antibody comprises a heavy chain variable regionsequence and a light chain variable region sequence an antibody providedherein and is selected from the group consisting of a Fab, Fab′,F(ab′)2, and scFv fragment.

In one embodiment, an antibody comprises a human immunoglobulin IgG₁heavy chain constant region, and wherein the amino acid sequence of theIgG₁ heavy chain constant region comprises a mutation selected from thegroup consisting of N297A, N297Q, D265A, and a combination thereof. Inone embodiment, the antibody comprises an IgG₁ heavy chain constantregion, wherein the amino acid sequence of the IgG₁ heavy chain constantregion comprises a mutation selected from the group consisting of D265A,P329A, and a combination thereof.

In one embodiment, an antibody that specifically binds to human OX40comprises: (a) a first antigen-binding domain that specifically binds tohuman OX40; and (b) a second antigen-binding domain that does notspecifically bind to an antigen expressed by a human immune cell.

In one embodiment, the antigen-binding domain that specifically binds tohuman OX40 comprises: (a) a first heavy chain variable domain (VH)comprising a VH complementarity determining region (CDR) 1 comprisingthe amino acid sequence of GSAMH (SEQ ID NO:4); a VH-CDR2 comprising theamino acid sequence of RIRSKANSYATAYAASVKG (SEQ ID NO:5); and a VH-CDR3comprising the amino acid sequence of GIYDSSGYDY (SEQ ID NO:6); and (b)a first light chain variable domain (VL) comprising a VL-CDR1 comprisingthe amino acid sequence of RSSQSLLHSNGYNYLD (SEQ ID NO:1); a VL-CDR2comprising the amino acid sequence of LGSNRAS (SEQ ID NO:2); and aVL-CDR3 comprising the amino acid sequence of MQALQTPLT (SEQ ID NO:3).In one embodiment, the antigen-binding domain that specifically binds tohuman OX40 specifically binds to the same epitope of human OX40 as anantibody comprising a VH comprising the amino acid sequence of SEQ IDNO:16 and a VL comprising the amino acid sequence of SEQ ID NO:15. Inone embodiment, the antigen-binding domain that specifically binds tohuman OX40 exhibits, as compared to binding to a human OX40 sequence ofSEQ ID NO:55, reduced or absent binding to a protein identical to SEQ IDNO:55 except for the presence of an amino acid mutation selected fromthe group consisting of: N60A, R62A, R80A, L88A, P93A, P99A, P115A, anda combination thereof. In one embodiment, the antigen-binding domainthat specifically binds to human OX40 comprises a VH and a VL, whereinthe VH comprises the amino acid sequence of SEQ ID NO:16. In oneembodiment, the antigen-binding domain that specifically binds to humanOX40 comprises a VH and a VL, wherein the VL comprises the amino acidsequence of SEQ ID NO:15.

In one embodiment, the second antigen-binding domain specifically bindsto a non-human antigen. In one embodiment, the second antigen-bindingdomain specifically binds to a viral antigen. In one embodiment, theviral antigen is a HIV antigen. In one embodiment, the secondantigen-binding domain specifically binds to chicken albumin or hen egglysozyme.

In one embodiment, an antibody that specifically binds to human OX40comprises (a) a first heavy chain variable domain (VH) comprising a VHcomplementarity determining region (CDR) 1 comprising the amino acidsequence of GSAMH (SEQ ID NO:4); a VH-CDR2 comprising the amino acidsequence of RIRSKANSYATAYAASVKG (SEQ ID NO:5); and a VH-CDR3 comprisingthe amino acid sequence of GIYDSSGYDY (SEQ ID NO:6); and (b) a firstlight chain variable domain (VL) comprising a VL-CDR1 comprising theamino acid sequence of RSSQSLLHSNGYNYLD (SEQ ID NO:1); a VL-CDR2comprising the amino acid sequence of LGSNRAS (SEQ ID NO:2); and aVL-CDR3 comprising the amino acid sequence of MQALQTPLT (SEQ ID NO:3).In one embodiment, the antigen-binding domain that specifically binds tohuman OX40 specifically binds to the same epitope of human OX40 as anantibody comprising a VH comprising the amino acid sequence of SEQ IDNO:16 and a VL comprising the amino acid sequence of SEQ ID NO:15. Inone embodiment, the antigen-binding domain that specifically binds tohuman OX40 exhibits, as compared to binding to a human OX40 sequence ofSEQ ID NO:55, reduced or absent binding to a protein identical to SEQ IDNO:55 except for the presence of an amino acid mutation selected fromthe group consisting of: N60A, R62A, R80A, L88A, P93A, P99A, P115A, anda combination thereof. In one embodiment, the antigen-binding domainthat specifically binds to human OX40 comprises a VH and a VL, whereinthe VH comprises the amino acid sequence of SEQ ID NO:16. In oneembodiment, the antigen-binding domain that specifically binds to humanOX40 comprises a VH and a VL, wherein the VL comprises the amino acidsequence of SEQ ID NO:15.

In one embodiment, the second heavy chain is a Fc fragment.

In one embodiment, the antigen-binding domain that specifically binds tohuman OX40 comprises a VH comprising an amino acid sequence that is atleast 75%, 80%, 85%, 90%, 95%, or 99% identical to the amino acidsequence of SEQ ID NO:16. In one embodiment, the antigen-binding domainthat specifically binds to human OX40 comprises a VH comprising theamino acid sequence of SEQ ID NO:16. In one embodiment, theantigen-binding domain that specifically binds to human OX40 comprises aVH comprising an amino acid sequence derived from a human IGHV3-73germline sequence.

In one embodiment, the antigen-binding domain that specifically binds tohuman OX40 comprises a VL comprising an amino acid sequence that is atleast 75%, 80%, 85%, 90%, 95%, or 99% identical to the amino acidsequence of SEQ ID NO:15. In one embodiment, the antigen-binding domainthat specifically binds to human OX40 comprises a VL-CDR3 comprising theamino acid sequence of SEQ ID NO:3. In one embodiment, theantigen-binding domain that specifically binds to human OX40 comprises aVL comprising the amino acid sequence of SEQ ID NO:15. In oneembodiment, the antigen-binding domain that specifically binds to humanOX40 comprises a light chain comprising the amino acid sequence of SEQID NO:20. In one embodiment, the antigen-binding domain thatspecifically binds to human OX40 comprises a light chain comprising theamino acid sequence of SEQ ID NO:50. In one embodiment, theantigen-binding domain that specifically binds to human OX40 comprises aVL comprising an amino acid sequence derived from a human IGKV2-28germline sequence.

In one embodiment, the antigen-binding domain that specifically binds tohuman OX40 comprises the VH and VL sequences set forth in SEQ ID NOs: 16and 15, respectively. In one embodiment, the antigen-binding domain thatspecifically binds to human OX40 comprises a heavy chain comprising theamino acid sequence of SEQ ID NO: 21. In one embodiment, theantigen-binding domain that specifically binds to human OX40 comprises aheavy chain comprising the amino acid sequence of SEQ ID NO: 60.

In one embodiment, the first antigen-binding domain and the secondantigen-binding domain comprise an identical mutation selected from thegroup consisting of N297A, N297Q, D265A, and a combination thereof. Inone embodiment, the first antigen-binding domain and the secondantigen-binding domain comprise an identical mutation selected from thegroup consisting of D265A, P329A, and a combination thereof. In oneembodiment, the antigen-binding domain that specifically binds to humanOX40 and the second heavy chain or fragment thereof comprise anidentical mutation selected from the group consisting of N297A, N297Q,D265A, and a combination thereof. In one embodiment, the antigen-bindingdomain that specifically binds to human OX40 and the second heavy chainor fragment thereof comprise an identical mutation selected from thegroup consisting of D265A, P329A, and a combination thereof.

In one embodiment, the antibody is antagonistic to human OX40. In oneembodiment, the antibody deactivates, reduces, or inhibits an activityof human OX40. In one embodiment, the antibody inhibits or reducesbinding of human OX40 to human OX40 ligand. In one embodiment, theantibody inhibits or reduces human OX40 signaling. In one embodiment,the antibody inhibits or reduces human OX40 signaling induced by humanOX40 ligand.

In one embodiment, the antibody comprises a detectable label.

In one embodiment, the present invention relates to an antibody of thepresent invention for use as a medicament.

In one embodiment, the present invention relates to an antibody of thepresent invention for use as a diagnostic.

In one embodiment, the present invention relates to the use of anantibody of the present invention for in vitro detection of OX40 in asample. In one embodiment, OX40 is human OX40.

In one embodiment, the present invention relates to the use of anantibody of the present invention for activating, enhancing, or inducingan activity of human OX40 in vitro. In one embodiment, the antibodyinduces CD4+ T cell proliferation in vitro.

In one aspect, provided herein are isolated nucleic acid moleculesencoding antibodies that specifically bind to OX40 (e.g., human OX40).In one embodiment, the nucleic acid molecule encodes the heavy chainvariable region or heavy chain of an anti-OX40 antibody provided herein.In one embodiment, the nucleic acid molecule encodes the light chainvariable region or light chain of an anti-OX40 antibody provided herein.In one embodiment, the nucleic acid molecule encodes the heavy chainvariable region or heavy chain of an anti-OX40 antibody provided hereinand the light chain variable region or light chain of the antibody. Inone embodiment, the nucleic acid molecule encodes a heavy chain variableregion comprising the amino acid sequence of SEQ ID NO: 16. In oneembodiment, the nucleic acid molecule encodes a light chain variableregion comprising the amino acid sequence of SEQ ID NO: 15. Isolatedantibodies encoded by such nucleic acid molecules are also providedherein.

In one aspect, provided herein are vectors comprising such nucleic acidmolecules.

In one aspect, provided herein are host cells comprising such nucleicacid molecules or such vectors. In one embodiment, the host cell isselected from the group consisting of E. coli, Pseudomonas, Bacillus,Streptomyces, yeast, CHO, YB/20, NS0, PER-C6, HEK-293T, NIH-3T3, HeLa,BHK, Hep G2, SP2/0, R1.1, B-W, L-M, COS 1, COS 7, BSC1, BSC40, BMT10cell, plant cell, insect cell, and human cell in tissue culture.

In one aspect, provided herein are methods of producing antibodies thatspecifically bind to OX40 (e.g., human OX40) comprising culturing suchhost cells so that the nucleic acid molecule is expressed and theantibody is produced.

In one embodiment, the present invention relates to an antibody of thepresent invention, a nucleic acid molecule of the invention, a vector ofthe invention, and/or a host cell of the invention, for use as amedicament.

In one embodiment, the present invention relates to an antibody of thepresent invention, a nucleic acid molecule of the invention, a vector ofthe invention, and/or a host cell of the invention, for use as adiagnostic.

In one embodiment, the present invention relates to the use of to anantibody of the present invention, a nucleic acid molecule of theinvention, a vector of the invention, and/or a host cell of theinvention, for the in vitro detection of OX40 in a sample. In oneembodiment, OX40 is human OX40.

In one embodiment, the present invention relates to the use of anantibody of the present invention for activating, enhancing, or inducingan activity of human OX40 in vitro. In one embodiment, the antibodyinduces CD4+ T cell proliferation in vitro.

In one aspect, provided herein are pharmaceutical compositionscomprising an antibody that specifically binds to OX40 provided herein,a nucleic acid molecule encoding an antibody that specifically binds toOX40 (e.g., human OX40), a vector comprising such a nucleic acidmolecule, or a host cell comprising such a nucleic acid molecule orvector.

In one aspect, provided herein are pharmaceutical compositionscomprising an antibody that specifically binds to OX40 provided herein,a nucleic acid molecule encoding an antibody that specifically binds toOX40, e.g., human OX40, a vector comprising such a nucleic acidmolecule, or a host cell comprising such a nucleic acid molecule orvector, for use as a medicament.

In one aspect, provided herein are pharmaceutical compositionscomprising an antibody that specifically binds to OX40 provided herein,a nucleic acid molecule encoding an antibody that specifically binds toOX40, e.g., human OX40, a vector comprising such a nucleic acidmolecule, or a host cell comprising such a nucleic acid molecule orvector, for use as a diagnostic.

In one aspect, provided herein are methods for modulating an immuneresponse in a subject comprising administering to the subject aneffective amount of an antibody, nucleic acid, vector, host cell, orpharmaceutical composition provided herein. In one embodiment, themethod is for enhancing or inducing the immune response of the subject.In one embodiment, modulating an immune response comprises enhancing orinducing the immune response of the subject.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for modulating an immuneresponse.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for enhancing or inducing animmune response. In one embodiment, the antibody is agonistic.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for modulating an immune responsein a subject.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for enhancing or inducing animmune response in a subject. In one embodiment, the antibody isagonistic.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for modulating an immune responsein a subject comprising administering to the subject an effective amountof an antibody, nucleic acid, vector, host cell, or pharmaceuticalcomposition of the invention.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for enhancing or inducing animmune response in a subject comprising administering to the subject aneffective amount of an antibody, nucleic acid, vector, host cell, orpharmaceutical composition of the invention. In one embodiment, theantibody is agonistic.

In one aspect, provided herein are methods for enhancing the expansionof T cells and T cell effector function in a subject comprisingadministering to the subject an effective amount of an antibody, nucleicacid, vector, host cell, or pharmaceutical composition provided herein.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for enhancing the expansion of Tcells and T cell effector function. In one embodiment, the antibody isagonistic.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for enhancing the expansion of Tcells and T cell effector function in a subject. In one embodiment, theantibody is agonistic.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for enhancing the expansion of Tcells and T cell effector function in a subject comprising administeringto the subject an effective amount of an antibody, nucleic acid, vector,host cell, and/or pharmaceutical composition of the invention. In oneembodiment, the antibody is agonistic.

In one aspect, provided herein are methods of treating cancer in asubject comprising administering to the subject an effective amount ofan antibody, nucleic acid, vector, host cell, or pharmaceuticalcomposition provided herein. In some embodiments, the cancer is selectedfrom the group consisting of melanoma, renal cancer, and prostatecancer. In some embodiments, the cancer is selected from the groupconsisting of melanoma, renal cancer, prostate cancer, colon cancer, andlung cancer. In some embodiments, the lung cancer is non-small cell lungcancer (NSCLC). In one instance, the method further comprisesadministering to the subject a checkpoint targeting agent. In oneinstance, the checkpoint targeting agent is selected from the groupconsisting of an antagonist anti-PD-1 antibody, an antagonist anti-PD-L1antibody, an antagonist anti-PD-L2 antibody, an antagonist anti-CTLA-4antibody, an antagonist anti-TIM-3 antibody, an antagonist anti-LAG-3antibody, an antagonist anti-CEACAM1 antibody, an agonist anti-GITRantibody, an agonist anti-CD137 antibody, and an agonist anti-OX40antibody.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for the treatment of cancer. Inone embodiment, the antibody is agonistic.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for the treatment of cancer in asubject. In one embodiment, the antibody is agonistic.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for the treatment of cancer in asubject comprising administering to the subject an effective amount ofan antibody, nucleic acid, vector, host cell, and/or pharmaceuticalcomposition of the invention. In one embodiment, the antibody isagonistic.

In one aspect, the present invention relates to (a) an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention and (b) a checkpoint targeting agent, for use as amedicament. In one embodiment, the antibody is agonistic.

In one aspect, the present invention relates to (a) an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention and (b) a checkpoint targeting agent, for use in amethod for the treatment of cancer. In one embodiment, the antibody isagonistic.

In one aspect, the present invention relates to a pharmaceuticalcomposition, kit or kit-of-parts comprising (a) an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention and (b) a checkpoint targeting agent.

The antibody as described herein can be used in combination with an IDOinhibitor for treating cancer. In one embodiment, the method furthercomprises administering to the subject an inhibitor ofindoleamine-2,3-dioxygenase (IDO). The IDO inhibitor as described hereinfor use in treating cancer is present in a solid dosage form of apharmaceutical composition such as a tablet, a pill or a capsule,wherein the pharmaceutical composition includes an IDO inhibitor and apharmaceutically acceptable excipient. As such, the antibody asdescribed herein and the IDO inhibitor as described herein can beadministered separately, sequentially or concurrently as separate dosageforms. In one embodiment, the antibody is administered parenterally, andthe IDO inhibitor is administered orally. In particular embodiments, theinhibitor is selected from the group consisting of epacadostat (IncyteCorporation), F001287 (Flexus Biosciences), indoximod (NewLinkGenetics), and NLG919 (NewLink Genetics). Epacadostat has been describedin PCT Publication No. WO 2010/005958, which is incorporated herein byreference in its entirety for all purposes. In one embodiment, theinhibitor is epacadostat. In another embodiment, the inhibitor isF001287. In another embodiment, the inhibitor is indoximod. In anotherembodiment, the inhibitor is NLG919.

In one aspect, the present invention relates to (a) an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention and (b) an IDO inhibitor, for use as a medicament.

In one aspect, the present invention relates to (a) an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention and (b) an IDO inhibitor, for use in a method for thetreatment of cancer. In one aspect, the present invention relates to acomposition, kit or kit-of-parts comprising (a) an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention and (b) an IDO inhibitor.

The antibody described herein can be used in combination with a vaccine.In a particular embodiment, the vaccine comprises a heat shock proteinpeptide complex (HSPPC), in which the HSPPC comprises a heat shockprotein (e.g., a gp96 protein, a hsp70 protein, or a hsc70 protein)complexed with one or more antigenic peptides (e.g., tumor-associatedantigenic peptides). In one embodiment, the heat shock protein is gp96protein and is complexed with a tumor-associated antigenic peptide. Inone embodiment, the heat shock protein is hsp70 or hsc70 protein and iscomplexed with a tumor-associated antigenic peptide. In one embodiment,the heat shock protein is gp96 protein and is complexed with atumor-associated antigenic peptide, wherein the HSPPC is derived from atumor obtained from a subject. In one embodiment, the heat shock proteinis hsp70 or hsc70 protein and is complexed with a tumor-associatedantigenic peptide, wherein the HSPPC is derived from a tumor obtainedfrom a subject.

In one aspect, the present invention relates to (a) an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention and (b) a vaccine, for use as a medicament. In oneembodiment, the antibody is agonistic.

In one aspect, the present invention relates to (a) an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention and (b) a vaccine, for use in a method for thetreatment of cancer. In one embodiment, the antibody is agonistic.

In one aspect, the present invention relates to a composition, kit orkit-of-parts comprising (a) an antibody, nucleic acid, vector, hostcell, and/or pharmaceutical composition of the present invention and (b)a vaccine. In one embodiment, the antibody is agonistic.

In some embodiments, the disclosure provides use of an antibody asdescribed herein in the manufacture of a medicament for the treatment ofcancer. In certain embodiments, the disclosure provides an antibody asdescribed herein for use in the treatment of cancer. In certainembodiments, the disclosure provides use of a pharmaceutical compositionas described herein in the manufacture of a medicament for the treatmentof cancer. In certain embodiments, the disclosure provides apharmaceutical composition as described herein for use in the treatmentof cancer.

In one aspect, provided herein are methods of treating an autoimmune orinflammatory disease or disorder in a subject comprising administeringto the subject an effective amount of an antibody, nucleic acid, vector,host cell, or pharmaceutical composition provided herein. In someembodiments, the disease or disorder is selected from the groupconsisting of: transplant rejection, vasculitis, asthma, rheumatoidarthritis, dermatitis, inflammatory bowel disease, uveitis, and lupus.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for the treatment of anautoimmune or inflammatory disease or disorder. In one embodiment, theantibody is antagonistic.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for the treatment of anautoimmune or inflammatory disease or disorder in a subject. In oneembodiment, the antibody is antagonistic.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for the treatment of anautoimmune or inflammatory disease or disorder in a subject comprisingadministering to the subject an effective amount of an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of theinvention. In one embodiment, the antibody is antagonistic.

In one aspect, provided herein are methods of treating an infectiousdisease in a subject comprising administering to the subject aneffective amount of an antibody, nucleic acid, vector, host cell, orpharmaceutical composition provided herein.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for the treatment of aninfectious disease. In one embodiment, the antibody is agonistic. In oneembodiment, the antibody is antagonistic.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for the treatment of aninfectious disease in a subject. In one embodiment, the antibody isagonistic. In one embodiment, the antibody is antagonistic.

In one aspect, the present invention relates to an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition of thepresent invention, for use in a method for the treatment of aninfectious disease in a subject comprising administering to the subjectan effective amount of an antibody, nucleic acid, vector, host cell,and/or pharmaceutical composition of the invention. In one embodiment,the antibody is agonistic. In one embodiment, the antibody isantagonistic.

In one embodiment of the methods provided herein, the subject is human.

In one aspect, provided herein are methods for detecting OX40 in asample comprising contacting said sample with the antibody providedherein.

In one aspect, provided herein are methods for in vitro detecting OX40in a sample comprising contacting said sample with the antibody providedherein. In one embodiment, OX40 is human OX40.

In one aspect, provided herein are methods for in vitro detecting OX40in a sample comprising contacting said sample with an antibody, nucleicacid, vector, host cell, and/or pharmaceutical composition providedherein. In one embodiment, OX40 is human OX40.

In one aspect, provided herein is the use of an antibody, nucleic acid,vector, host cell, and/or pharmaceutical composition provided herein,preferably of an antibody provided herein, for in vitro detecting OX40in a sample.

In one aspect, provided herein is an antibody, nucleic acid, vector,host cell, and/or pharmaceutical composition provided herein, preferablyan antibody provided herein, for use in the detection of OX40 in asubject. In one embodiment, the subject is a human.

In one aspect, provided herein are kits comprising an antibody thatspecifically binds to OX40 provided herein, a nucleic acid moleculeencoding an antibody that specifically binds to OX40 (e.g., human OX40),a vector comprising such a nucleic acid molecule, a host cell comprisingsuch a nucleic acid molecule or vector, or a pharmaceutical compositioncomprising such an antibody, nucleic acid molecule, vector, or host celland a) a detection reagent, b) an OX40 antigen, c) a notice thatreflects approval for use or sale for human administration, or d) acombination thereof.

4. BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A, 1B, 1C, 1D, and 1E: FIG. 1A is a pair of histograms showingthe binding of the anti-OX40 antibody pab1949 and an isotype control toactivated human CD4+ T cells and CD8+ T cells. FIG. 1B is a pair ofhistograms showing the binding of pab1949-1 and an isotype control tonon-stimulated and stimulated (using anti-CD3 antibody) CD4+ T cells.FIG. 1C is a graph showing the binding of a dose titration of pab1949-1or an isotype control to activated human CD4+ T cells. FIG. 1D is a setof histograms measuring the binding of pab1949-1 and an isotype controlto human non-stimulated blood-derived immune cell populations. FIG. 1Eis a histogram of the binding of pab1949 and an isotype control toactivated cynomolgus monkey (Macaca fascicularis) CD4+ T cells.

FIGS. 2A, 2B, and 2C are graphs of results of suboptimal CD3 stimulationassays to assess the effects of stimulation of anti-OX40 antibodiespab1949 (FIGS. 2A and 2C) and pab2044 (FIG. 2B) on enriched CD4+ T cellproliferation. The antibody pab1949 is a human IgG₁ antibody. Theantibody pab2044 shares the same heavy chain variable region and thesame light chain as pab1949 but comprises a human IgG₄ constant region.Cell proliferation (CFSE; x-axis) is shown for each antibody tested:IgG₁ isotype control, pab1949, and anti-CD28 antibody as a positivecontrol in FIG. 2A; and IgG₄ isotype control, pab2044, and anti-CD28antibody in FIG. 2B. FIG. 2C is a line graph showing the titration ofthe anti-OX40 antibody pab1949 (0.002, 0.02, 0.2, 2, and 20 μg/ml) andthe effect of the antibody on enriched CD4+ T cell proliferation undersuboptimal anti-CD3 stimulation.

FIGS. 3A, 3B, 3C, 3D, 3E, and 3F are representative results fromanalyses of the production of IFNγ and TNFα cytokines induced by theanti-OX40 antibody pab1949 or pab1949-1 in combination with varyingsuboptimal concentrations of anti-CD3 antibody and IL-2. In FIGS. 3A-3C,PBMCs from four different donors were tested: donor KM, donor TM, donorGS, and donor SB. FIGS. 3A and 3B are plots showing intracellularcytokine staining (IFNγ and TNFα) of CD4+ T cells and CD8+ T cells fromdonor SB (FIG. 3A) and donor GS (FIG. 3B). The percentage of IFNγ+ TNFα+polyfunctional CD4+ T cells and CD8+ T cells or TNFα+ monofunctionalCD4+ T cells and CD8+ T cells is plotted for the anti-OX40 antibodypab1949 or an isotype control (FIG. 3C). The percentages shown in FIG.3C represent the highest response generated under three differentanti-CD3 antibody concentrations. Error bars represent standarddeviation (n=2). FIGS. 3D, 3E, and 3F are a set of graphs showing thepercentage of TNFα+ CD4+ T cells (FIG. 3D), IFNγ+ TNFα+ polyfunctionalCD8+ T cells (FIG. 3E), and IFNγ+ CD8+ T cells (FIG. 3F) induced by adose titration of the anti-OX40 antibody pab1949-1 or an IgG₁ isotypecontrol antibody in cells derived from PBMCs of donor GS in a similarsuboptimal anti-CD3 stimulation assay.

FIGS. 4A, 4B, and 4C are a set of graphs showing results of a suboptimalanti-CD3 stimulation assay using cells derived from PBMCs of donors 1,2, 4, 5, 7, 8, 9, and 10. The percentage of IFNγ+, TNFα+, or IFNγ+ TNFα+polyfunctional CD4+ or CD8+ T cells is plotted against a range ofantibody concentrations of pab1949-1 or an IgG₁ isotype controlantibody.

FIG. 5A is a set of bar graphs showing the effect of the anti-OX40antibody pab1949 or an isotype control on the secretion of a panel ofcytokines (IL-2, TNFα, IL-10, IL-4, and IL-13) in a suboptimal anti-CD3stimulation assay using PBMCs from donor SB and donor GS. PBMCs fromhealthy donors were activated using various suboptimal concentrations ofanti-CD3 antibody (clone SP34), IL2 (20 U/ml), and 5 μg/ml of anti-OX40antibody or an IgG₁ isotype control and cytokines were measured aftereither 4 days (SB #1A) or 3 days (SB #1B, SB #2, and GS) uponstimulation. The bars in FIG. 5A represent the highest cytokinesecretion induced by all the anti-CD3 concentrations tested at ananti-OX40 antibody concentration of 5 μg/ml. Errors bars representstandard deviation (n=2). FIGS. 5B, 5C, and 5D are a set of graphsshowing the amount of secreted cytokines (TNFα, IL-10, or IL-13) inducedby various concentrations of pab1949-1 or an IgG₁ isotype controlantibody in cells derived from PBMCs of donor GS in the presence ofsuboptimal concentrations of an anti-CD3 antibody.

FIGS. 6A, 6B, and 6C are a set of graphs showing the amount of secretedGM-CSF induced by a dose titration of pab1949-1 or an IgG₁ isotypecontrol antibody in cells derived from PBMCs of donors 1-10 in asuboptimal anti-CD3 stimulation assay. ECL refers toelectrochemiluminescence.

FIGS. 7A, 7B, and 7C are similar to FIGS. 6A, 6B, and 6C, showing theamount of secreted IL-2 induced by a dose titration of pab1949-1 or anIgG₁ isotype control antibody. ECL refers to electrochemiluminescence.

FIGS. 8A, 8B, and 8C are similar to FIGS. 6A, 6B, and 6C, showing theamount of secreted TNFβ induced by a dose titration of pab1949-1 or anIgG₁ isotype control antibody.

FIGS. 9A and 9B are bar graphs showing the production of IL-2 (FIG. 9A)and IL-10 (FIG. 9B) induced by either soluble or crosslinked (usinganti-Fc F(ab′)2) pab1949-1 or an IgG₁ isotype control antibody in Tregulatory cells (Treg) and T effector cells (Teff) co-cultured at aratio of 1:3 (Treg:Teff).

FIGS. 10A, 10B, 10C, 10D, 10E, 10F, and 10G are graphs depicting thefunctional activity of anti-OX40 antibodies on primary human PBMCs uponStaphylococcus Enterotoxin A (SEA) stimulation. Human PBMCs werestimulated with SEA in the absence or presence of a fixed concentration(10 μg/ml) or varying concentrations of anti-OX40 antibody or isotypecontrol and assessed for IL-2 or IL-10 cytokine secretion. The anti-OX40antibodies tested include pab1949, pab1949-1, pab2193-1,pab1949-1-N297A, and the reference antibodies pab1784 and pab2045. Thefold change of IL-2 (FIG. 10A) and IL-10 (FIG. 10B) at an anti-OX40antibody concentration of 10 μg/ml is plotted for the tested antibodies.FIGS. 10C, 10D, and 10E are dose-response curves showing the fold changeof IL-2 production at different concentrations of pab1949, pab1949-1, orthe reference antibodies pab1784 and pab2045. Statistical significancewas determined by student's t test compared to the isotype controlsamples indicated by asterisk. Error bars represent standard deviationfrom triplicate repeats. * in FIG. 10A represents p<0.001. * in FIG. 10Brepresents p<0.01. FIG. 10F is a graph showing IL-2 production inducedby a dose titration of pab1949-1, pab2193-1, an IgG₁ isotype controlantibody, or an IgG₂ isotype control antibody. FIG. 10G is a graphshowing IL-2 production in response to a dose titration of pab1949-1,pab1949-1-N297A, or an IgG₁ isotype control antibody.

FIGS. 11A and 11B are results from an assay in which soluble (solublecondition, FIG. 11A) or crosslinked (complexed condition, FIG. 11B)pab1949-1 or an IgG₁ isotype control antibody were tested using an OX40NF-κB-luciferase reporter cell line. Relative light units (RLU) areplotted against various antibody concentrations tested.

FIGS. 12A and 12B are results from reporter assays in which anti-OX40antibodies were tested for their ability to activate reporter cellsexpressing FcγRIIIA (FIG. 12A) or the FcγRIIA^(H131) variant (FIG. 12B)when the antibodies were bound to OX40-expressing target cells. In FIG.12A, Δ RLU values are plotted against various concentrations ofpab1949-1 and pab2044-1. Δ RLU represents the RLU of the anti-OX40antibody minus that of the isotype control. In FIG. 12B, the RLU valuesare plotted against increasing concentrations of pab1949-1,pab1949-1-S267E/L328F, pab2193-1, an IgG₁ isotype control antibody, oran IgG₂ isotype control antibody.

FIG. 13A is a bar graph showing ΔMFI of human OX40 on nTregs, CD4+ Tcells or CD8+ T cells from healthy donors activated byanti-CD3/anti-CD28 beads, as measured by flow cytometry. ΔMFI representsthe MFI of the anti-OX40 antibody minus the MFI of an isotype control.The anti-OX40 antibody used was a PE-conjugated mouse anti-human OX40antibody (Biolegend: ACT35; Catalogue: 350004; Lot: B181090). FIG. 13Bis a bar graph showing ΔMFI of human OX40 on activated nTregs and Teffector cells from two healthy donors. The cells were stained with acommercial anti-OX40 antibody (BER-ACT35 clone) or an isotype controlantibody and analyzed using flow cytometry. FIG. 13C is a graphexamining the anti-OX40 antibody pab1949 using an Fc gamma receptor IIIA(FcγRIIIA) reporter cell line. Jurkat NFAT-luciferase reporter cellsoverexpressing FcγRIIIA (158 V/V polymorphism) were co-cultured withactivated primary nTregs and T effector cells for 20 hours at 37° C. inthe presence of pab1949 or an isotype control. The relative light units(RLU) were recorded after 20 hours, representing FcγRIIIA binding. Δ RLUrepresents the RLU of the anti-OX40 antibody minus that of the isotypecontrol. The error bars represent standard deviation (n=2). The datashown are representative of experiments using cells from three donors.FIG. 13D is similar to FIG. 13C, showing results from a study testingpab1949-1 using a modified protocol.

FIG. 14A is a set of histograms showing the surface expression of OX40measured by flow cytometry. Samples were collected from the blood ofhealthy human donors (a-c, n=3) or from tumor tissues of non-small celllung cancer patients (NSCLC) (d-f, n=3). The cell populations weredefined as: Tconv (CD3+, CD4+, CD8a−, CD25low, and FOXP3−) or Treg(CD3+, CD4+, CD8a−, CD25high, and FOXP3+). FIG. 14B is a pair ofhistograms from a study similar to that depicted in FIG. 14A measuringsurface OX40 expression in CD8+ or CD4+ T cells, or Treg cells fromendometrial cancer samples. FIG. 14C is a bar graph showing OX40expression on Treg cells and Teff cells across various tumor types. FIG.14D is a table summarizing OX40 expression in tumor-associated CD4+ Teffcells and Treg cells. “−” represents negative/no expression, “+”represents weak expression, “++” represents moderate expression, and“+++” represents high expression.

FIGS. 15A and 15B are a set of graphs showing the amount of secretedGM-CSF induced by a dose titration of pab1949-1 or an IgG₁ isotypecontrol antibody in cells derived from cynomolgus PBMCs. Note that Cyno2 and Cyno 9 refer to PBMCs from a same cynomolgus monkey tested inindependent experiments. All the other PBMC samples were collected fromdifferent cynomolgus donors.

FIGS. 16A and 16B are similar to FIGS. 15A and 15B, showing the amountof secreted IL-17 induced by a dose titration of pab1949-1 or an IgG₁isotype control antibody.

FIGS. 17A and 17B are similar to FIGS. 15A and 15B, showing the amountof secreted TNFβ induced by a dose titration of pab1949-1 or an IgG₁isotype control antibody.

FIGS. 18A and 18B are similar to FIGS. 15A and 15B, showing the amountof secreted IL-5 induced by a dose titration of pab1949-1 or an IgG₁isotype control antibody.

FIGS. 19A and 19B are similar to FIGS. 15A and 15B, showing the amountof secreted IL-10 induced by a dose titration of pab1949-1 or an IgG₁isotype control antibody.

FIGS. 20A and 20B are a pair of graphs showing results from an assayexamining the functional activity of the anti-OX40 antibody pab1949-1 onprimary cynomolgus PBMCs upon Staphylococcus Enterotoxin A (SEA)stimulation. The amount of IL-2 secreted by PBMCs from two cynomolgusdonors is plotted against a dose titration of pab1949-1 or an IgG₁isotype control antibody.

FIG. 21 is a table summarizing the binding of the monoclonal anti-OX40antibodies pab1949-1 and pab1928 to 1624-5 cells expressing human OX40alanine mutants.

5. DETAILED DESCRIPTION

Provided herein are antibodies (e.g., monoclonal antibodies) thatspecifically bind to OX40 (e.g., human OX40) and modulate OX40 activity.For example, in one aspect, provided herein are antibodies thatspecifically bind to OX40 and enhance, induce, or increase one or moreOX40 activities. For example, in another aspect, provided herein areantibodies that specifically bind to OX40 (e.g., human OX40) anddeactivate, reduce, or inhibit one or more OX40 activities. In aspecific embodiment, the antibodies are isolated.

Also provided are isolated nucleic acids (polynucleotides), such ascomplementary DNA (cDNA), encoding such antibodies. Further provided arevectors (e.g., expression vectors) and cells (e.g., host cells)comprising nucleic acids (polynucleotides) encoding such antibodies.Also provided are methods of making such antibodies. In other aspects,provided herein are methods and uses for inducing, increasing orenhancing an OX40 activity, and treating certain conditions, such ascancer. Further provided are methods and uses for deactivating,reducing, or inhibiting an OX40 (e.g., human OX40) activity, andtreating certain conditions, such as inflammatory or autoimmune diseasesand disorders. Related compositions (e.g., pharmaceutical compositions),kits, and detection methods are also provided.

5.1 Terminology

As used herein, the terms “about” and “approximately,” when used tomodify a numeric value or numeric range, indicate that deviations of 5%to 10% above and 5% to 10% below the value or range remain within theintended meaning of the recited value or range.

As used herein, B is a “substantially increasing function” of A over aspecified domain of A values if B substantially increases as A increasesover the specified domain, e.g., in a given experiment, or using meanvalues from multiple experiments. This definition allows for a value ofB corresponding to a specified value of A to be up to 1%, 2%, 3%, 4%,5%, 10%, 15%, or 20% lower relative to a value of B corresponding to anylower value of A.

As used herein, the terms “antibody” and “antibodies” are terms of artand can be used interchangeably herein and refer to a molecule with anantigen-binding site that specifically binds an antigen.

Antibodies can include, for example, monoclonal antibodies,recombinantly produced antibodies, human antibodies, humanizedantibodies, resurfaced antibodies, chimeric antibodies, immunoglobulins,synthetic antibodies, tetrameric antibodies comprising two heavy chainand two light chain molecules, an antibody light chain monomer, anantibody heavy chain monomer, an antibody light chain dimer, an antibodyheavy chain dimer, an antibody light chain-antibody heavy chain pair,intrabodies, heteroconjugate antibodies, single domain antibodies,monovalent antibodies, single chain antibodies or single-chain Fvs(scFv), camelized antibodies, affybodies, Fab fragments, F(ab′)2fragments, disulfide-linked Fvs (sdFv), anti-idiotypic (anti-Id)antibodies (including, e.g., anti-anti-Id antibodies), bispecificantibodies, and multi-specific antibodies. In certain embodiments,antibodies described herein refer to polyclonal antibody populations.Antibodies can be of any type (e.g., IgG, IgE, IgM, IgD, IgA, or IgY),any class (e.g., IgG₁, IgG₂, IgG₃, IgG₄, IgA₁, or IgA₂), or any subclass(e.g., IgG_(2a) or IgG_(2b)) of immunoglobulin molecule. In certainembodiments, antibodies described herein are IgG antibodies, or a class(e.g., human IgG₁, IgG₂, or IgG₄) or subclass thereof. In a specificembodiment, the antibody is a humanized monoclonal antibody. In anotherspecific embodiment, the antibody is a human monoclonal antibody, e.g.,that is an immunoglobulin. In certain embodiments, an antibody describedherein is an IgG₁, IgG₂, or IgG₄ antibody.

As used herein, the terms “antigen-binding domain,” “antigen-bindingregion,” “antigen-binding site,” and similar terms refer to the portionof antibody molecules which comprises the amino acid residues thatconfer on the antibody molecule its specificity for the antigen (e.g.,the complementarity determining regions (CDR)). The antigen-bindingregion can be derived from any animal species, such as rodents (e.g.,mouse, rat, or hamster) and humans.

As used herein, the terms “variable region” or “variable domain” areused interchangeably and are common in the art. The variable regiontypically refers to a portion of an antibody, generally, a portion of alight or heavy chain, typically about the amino-terminal 110 to 120amino acids or 110 to 125 amino acids in the mature heavy chain andabout 90 to 115 amino acids in the mature light chain, which differextensively in sequence among antibodies and are used in the binding andspecificity of a particular antibody for its particular antigen. Thevariability in sequence is concentrated in those regions calledcomplementarity determining regions (CDRs) while the more highlyconserved regions in the variable domain are called framework regions(FR). Without wishing to be bound by any particular mechanism or theory,it is believed that the CDRs of the light and heavy chains are primarilyresponsible for the interaction and specificity of the antibody withantigen. In certain embodiments, the variable region is a human variableregion. In certain embodiments, the variable region comprises rodent ormurine CDRs and human framework regions (FRs). In particularembodiments, the variable region is a primate (e.g., non-human primate)variable region. In certain embodiments, the variable region comprisesrodent or murine CDRs and primate (e.g., non-human primate) frameworkregions (FRs).

The terms “VL” and “VL domain” are used interchangeably to refer to thelight chain variable region of an antibody.

The terms “VH” and “VH domain” are used interchangeably to refer to theheavy chain variable region of an antibody.

The term “Kabat numbering” and like terms are recognized in the art andrefer to a system of numbering amino acid residues in the heavy andlight chain variable regions of an antibody, or an antigen-bindingportion thereof. In certain aspects, the CDRs of an antibody can bedetermined according to the Kabat numbering system (see, e.g., Kabat E A& Wu T T (1971) Ann NY Acad Sci 190: 382-391 and Kabat E A et al.,(1991) Sequences of Proteins of Immunological Interest, Fifth Edition,U.S. Department of Health and Human Services, NIH Publication No.91-3242). Using the Kabat numbering system, CDRs within an antibodyheavy chain molecule are typically present at amino acid positions 31 to35, which optionally can include one or two additional amino acids,following 35 (referred to in the Kabat numbering scheme as 35A and 35B)(CDR1), amino acid positions 50 to 65 (CDR2), and amino acid positions95 to 102 (CDR3). Using the Kabat numbering system, CDRs within anantibody light chain molecule are typically present at amino acidpositions 24 to 34 (CDR1), amino acid positions 50 to 56 (CDR2), andamino acid positions 89 to 97 (CDR3). In a specific embodiment, the CDRsof the antibodies described herein have been determined according to theKabat numbering scheme.

As used herein, the term “constant region” or “constant domain” areinterchangeable and have its meaning common in the art. The constantregion is an antibody portion, e.g., a carboxyl terminal portion of alight and/or heavy chain which is not directly involved in binding of anantibody to antigen but which can exhibit various effector functions,such as interaction with the Fc receptor. The constant region of animmunoglobulin molecule generally has a more conserved amino acidsequence relative to an immunoglobulin variable domain.

As used herein, the term “heavy chain” when used in reference to anantibody can refer to any distinct type, e.g., alpha (α), delta (δ),epsilon (ε), gamma (γ), and mu (μ), based on the amino acid sequence ofthe constant domain, which give rise to IgA, IgD, IgE, IgG, and IgMclasses of antibodies, respectively, including subclasses of IgG, e.g.,IgG₁, IgG₂, IgG₃, and IgG₄.

As used herein, the term “light chain” when used in reference to anantibody can refer to any distinct type, e.g., kappa (κ) or lambda (λ)based on the amino acid sequence of the constant domains. Light chainamino acid sequences are well known in the art. In specific embodiments,the light chain is a human light chain.

“Binding affinity” generally refers to the strength of the sum total ofnon-covalent interactions between a single binding site of a molecule(e.g., an antibody) and its binding partner (e.g., an antigen). Unlessindicated otherwise, as used herein, “binding affinity” refers tointrinsic binding affinity which reflects a 1:1 interaction betweenmembers of a binding pair (e.g., antibody and antigen). The affinity ofa molecule X for its partner Y can generally be represented by thedissociation constant (K_(D)). Affinity can be measured and/or expressedin a number of ways known in the art, including, but not limited to,equilibrium dissociation constant (K_(D)), and equilibrium associationconstant (K_(A)). The K_(D) is calculated from the quotient ofk_(off)/k_(on), whereas K_(A) is calculated from the quotient ofk_(on)/k_(off). k_(on) refers to the association rate constant of, e.g.,an antibody to an antigen, and k_(off) refers to the dissociation of,e.g., an antibody to an antigen. The k_(on) and k_(off) can bedetermined by techniques known to one of ordinary skill in the art, suchas BIAcore® or KinExA.

As used herein, a “conservative amino acid substitution” is one in whichthe amino acid residue is replaced with an amino acid residue having asimilar side chain. Families of amino acid residues having side chainshave been defined in the art. These families include amino acids withbasic side chains (e.g., lysine, arginine, histidine), acidic sidechains (e.g., aspartic acid, glutamic acid), uncharged polar side chains(e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine,cysteine, tryptophan), nonpolar side chains (e.g., alanine, valine,leucine, isoleucine, proline, phenylalanine, methionine), beta-branchedside chains (e.g., threonine, valine, isoleucine) and aromatic sidechains (e.g., tyrosine, phenylalanine, tryptophan, histidine). Incertain embodiments, one or more amino acid residues within a CDR(s) orwithin a framework region(s) of an antibody can be replaced with anamino acid residue with a similar side chain.

As used herein, an “epitope” is a term in the art and refers to alocalized region of an antigen to which an antibody can specificallybind. An epitope can be, for example, contiguous amino acids of apolypeptide (linear or contiguous epitope) or an epitope can, forexample, come together from two or more non-contiguous regions of apolypeptide or polypeptides (conformational, non-linear, discontinuous,or non-contiguous epitope). In certain embodiments, the epitope to whichan antibody binds can be determined by, e.g., NMR spectroscopy, X-raydiffraction crystallography studies, ELISA assays, hydrogen/deuteriumexchange coupled with mass spectrometry (e.g., liquid chromatographyelectrospray mass spectrometry), array-based oligo-peptide scanningassays, and/or mutagenesis mapping (e.g., site-directed mutagenesismapping). For X-ray crystallography, crystallization may be accomplishedusing any of the known methods in the art (e.g., Giegé R et al., (1994)Acta Crystallogr D Biol Crystallogr 50(Pt 4): 339-350; McPherson A(1990) Eur J Biochem 189: 1-23; Chayen N E (1997) Structure 5:1269-1274; McPherson A (1976) J Biol Chem 251: 6300-6303). Antibody:antigen crystals can be studied using well known X-ray diffractiontechniques and can be refined using computer software such as X-PLOR(Yale University, 1992, distributed by Molecular Simulations, Inc.; see,e.g., Meth Enzymol (1985) volumes 114 & 115, eds Wyckoff H W et al.;U.S. 2004/0014194), and BUSTER (Bricogne G (1993) Acta Crystallogr DBiol Crystallogr 49(Pt 1): 37-60; Bricogne G (1997) Meth Enzymol 276A:361-423, ed Carter C W; Roversi P et al., (2000) Acta Crystallogr D BiolCrystallogr 56(Pt 10): 1316-1323). Mutagenesis mapping studies can beaccomplished using any method known to one of skill in the art. See,e.g., Champe M et al., (1995) J Biol Chem 270: 1388-1394 and CunninghamB C & Wells J A (1989) Science 244: 1081-1085 for a description ofmutagenesis techniques, including alanine scanning mutagenesistechniques. In a specific embodiment, the epitope of an antibody isdetermined using alanine scanning mutagenesis studies.

As used herein, the terms “immunospecifically binds,”“immunospecifically recognizes,” “specifically binds,” and “specificallyrecognizes” are analogous terms in the context of antibodies and referto molecules that bind to an antigen (e.g., epitope or immune complex)as such binding is understood by one skilled in the art. For example, amolecule that specifically binds to an antigen can bind to otherpeptides or polypeptides, generally with lower affinity as determinedby, e.g., immunoassays, BIAcore®, KinExA 3000 instrument (SapidyneInstruments, Boise, Id.), or other assays known in the art. In aspecific embodiment, molecules that immunospecifically bind to anantigen bind to the antigen with a K_(A) that is at least 2 logs, 2.5logs, 3 logs, 4 logs or greater than the K_(A) when the molecules bindnon-specifically to another antigen. In the context of antibodies withan anti-OX40 antigen-binding domain and a second antigen-binding domainthat does not specifically bind to an antigen expressed by a humanimmune cell, the terms “immunospecifically binds,” “immunospecificallyrecognizes,” “specifically binds,” and “specifically recognizes” referto antibodies that have distinct specificities for more than one antigen(i.e., OX40 and the antigen associated with the second antigen-bindingdomain).

In another specific embodiment, molecules that immunospecifically bindto an antigen do not cross react with other proteins under similarbinding conditions. In another specific embodiment, molecules thatimmunospecifically bind to an antigen do not cross react with othernon-OX40 proteins. In a specific embodiment, provided herein is anantibody that binds to OX40 with higher affinity than to anotherunrelated antigen. In certain embodiments, provided herein is anantibody that binds to OX40 (e.g., human OX40) with a 20%, 25%, 30%,35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% orhigher affinity than to another, unrelated antigen as measured by, e.g.,a radioimmunoassay, surface plasmon resonance, or kinetic exclusionassay. In a specific embodiment, the extent of binding of an anti-OX40antibody described herein to an unrelated, non-OX40 protein is less than10%, 15%, or 20% of the binding of the antibody to OX40 protein asmeasured by, e.g., a radioimmunoassay.

In a specific embodiment, provided herein is an antibody that binds tohuman OX40 with higher affinity than to another species of OX40. Incertain embodiments, provided herein is an antibody that binds to humanOX40 with a 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%,65%, 70% or higher affinity than to another species of OX40 as measuredby, e.g., a radioimmunoassay, surface plasmon resonance, or kineticexclusion assay. In a specific embodiment, an antibody described herein,which binds to human OX40, will bind to another species of OX40 proteinwith less than 10%, 15%, or 20% of the binding of the antibody to thehuman OX40 protein as measured by, e.g., a radioimmunoassay, surfaceplasmon resonance, or kinetic exclusion assay.

As used herein, the terms “OX40 receptor” or “OX40” or “OX40polypeptide” refer to OX40 including, but not limited to, native OX40,an isoform of OX40, or an interspecies OX40 homolog of OX40. OX40 isalso known as tumor necrosis factor receptor superfamily member 4(TNFRSF4), ACT35, CD134, IMD16, and TXGP1L. GenBank™ accession numbersBC105070 and BC105072 provide human OX40 nucleic acid sequences. Refseqnumber NP 003318.1 provides the amino acid sequence of human OX40. Theimmature amino acid sequence of human OX40 is provided as SEQ ID NO: 17.The mature amino acid sequence of human OX40 is provided as SEQ ID NO:55. Human OX40 is designated GeneID: 7293 by Entrez Gene. RefSeq numbersXM_005545122.1 and XP_005545179.1 provide predicted cynomolgus OX40nucleic acid sequences and amino acid sequences, respectively. A solubleisoform of human OX40 has also been reported (Taylor L et al., (2001) JImmunol Methods 255: 67-72). As used herein, the term “human OX40”refers to OX40 comprising the polypeptide sequence of SEQ ID NO:55.

As used herein, the terms “OX40 ligand” and “OX40L” refer to tumornecrosis factor ligand superfamily member 4 (TNFSF4). OX40L is otherwiseknown as CD252, GP34, TXGP1, and CD134L. GenBank™ accession numbersD90224.1 and AK297932.1 provide exemplary human OX40L nucleic acidsequences. RefSeq number NP_003317.1 and Swiss-Prot accession numberP23510-1 provide exemplary human OX40L amino acid sequences forisoform 1. RefSeq number NP_001284491.1 and Swiss-Prot accession numberP23510-2 provide exemplary human OX40L amino acid sequences for isoform2. Human OX40L is designated GeneID: 7292 by Entrez Gene. In aparticular embodiment, the OX40L is human OX40L isoform 1 of SEQ ID NO:42 or isoform 2 of SEQ ID NO: 43.

As used herein, the term “host cell” can be any type of cell, e.g., aprimary cell, a cell in culture, or a cell from a cell line. In specificembodiments, the term “host cell” refers to a cell transfected with anucleic acid molecule and the progeny or potential progeny of such acell. Progeny of such a cell may not be identical to the parent celltransfected with the nucleic acid molecule, e.g., due to mutations orenvironmental influences that may occur in succeeding generations orintegration of the nucleic acid molecule into the host cell genome.

As used herein, the term “effective amount” in the context of theadministration of a therapy to a subject refers to the amount of atherapy that achieves a desired prophylactic or therapeutic effect.Examples of effective amounts are provided in Section 5.5.1.3, infra.

As used herein, the terms “subject” and “patient” are usedinterchangeably. The subject can be an animal. In some embodiments, thesubject is a mammal such as a non-primate (e.g., cow, pig, horse, cat,dog, rat, etc.) or a primate (e.g., monkey or human), most preferably ahuman. In some embodiments, the subject is a cynomolgus monkey. Incertain embodiments, such terms refer to a non-human animal (e.g., anon-human animal such as a pig, horse, cow, cat, or dog). In someembodiments, such terms refer to a pet or farm animal. In specificembodiments, such terms refer to a human.

As used herein, the binding between a test antibody and a first antigenis “substantially weakened” relative to the binding between the testantibody and a second antigen if the binding between the test antibodyand the first antigen is reduced by at least 30%, 40%, 50%, 60%, 70%, or80% relative to the binding between the test antibody and the secondantigen, as measured in, e.g., a flow cytometry analysis.

The determination of “percent identity” between two sequences (e.g.,amino acid sequences or nucleic acid sequences) can also be accomplishedusing a mathematical algorithm. A specific, non-limiting example of amathematical algorithm utilized for the comparison of two sequences isthe algorithm of Karlin S & Altschul S F (1990) PNAS 87: 2264-2268,modified as in Karlin S & Altschul S F (1993) PNAS 90: 5873-5877. Suchan algorithm is incorporated into the NBLAST and XBLAST programs ofAltschul S F et al., (1990) J Mol Biol 215: 403. BLAST nucleotidesearches can be performed with the NBLAST nucleotide program parametersset, e.g., for score=100, wordlength=12 to obtain nucleotide sequenceshomologous to a nucleic acid molecules described herein. BLAST proteinsearches can be performed with the XBLAST program parameters set, e.g.,to score 50, wordlength=3 to obtain amino acid sequences homologous to aprotein molecule described herein. To obtain gapped alignments forcomparison purposes, Gapped BLAST can be utilized as described inAltschul S F et al., (1997) Nuc Acids Res 25: 3389 3402. Alternatively,PSI BLAST can be used to perform an iterated search which detectsdistant relationships between molecules (Id.). When utilizing BLAST,Gapped BLAST, and PSI Blast programs, the default parameters of therespective programs (e.g., of XBLAST and NBLAST) can be used (see, e.g.,National Center for Biotechnology Information (NCBI) on the worldwideweb, ncbi.nlm.nih.gov). Another specific, non-limiting example of amathematical algorithm utilized for the comparison of sequences is thealgorithm of Myers and Miller, 1988, CABIOS 4:11 17. Such an algorithmis incorporated in the ALIGN program (version 2.0) which is part of theGCG sequence alignment software package. When utilizing the ALIGNprogram for comparing amino acid sequences, a PAM120 weight residuetable, a gap length penalty of 12, and a gap penalty of 4 can be used.

The percent identity between two sequences can be determined usingtechniques similar to those described above, with or without allowinggaps. In calculating percent identity, typically only exact matches arecounted.

As used herein, the term “antigen-binding domain that does not bind toan antigen expressed by a human immune cell” means that theantigen-binding domain does not bind to an antigen expressed by anyhuman cell of hematopoietic origin that plays a role in the immuneresponse. Immune cells include lymphocytes, such as B cells and T cells;natural killer cells; and myeloid cells, such as monocytes, macrophages,eosinophils, mast cells, basophils, and granulocytes. For example, sucha binding domain would not bind to OX40, or any other members of the TNFreceptor superfamily that are expressed by a human immune cell. However,the antigen-binding domain can bind to an antigen such as, but notlimited to, an antigen expressed in other organisms and not humans(i.e., a non-human antigen); an antigen that is not expressed bywild-type human cells; or a viral antigen, including, but not limitedto, an antigen from a virus that does not infect human cells, or a viralantigen that is absent in an uninfected human immune cell.

5.2 Antibodies

In a specific aspect, provided herein are antibodies (e.g., monoclonalantibodies, such as chimeric, humanized, or human antibodies) whichspecifically bind to OX40 (e.g., human OX40).

In certain embodiments, an antibody described herein binds to human CD4+T cells and human CD8+ T cells. In certain embodiments, an antibodydescribed herein binds to human CD4+ cells and cynomolgus monkey CD4+ Tcells.

In a particular embodiment, an antibody described herein, whichspecifically binds to OX40 (e.g., human OX40), comprises a light chainvariable region (VL) comprising:

(a) a VL CDR1 comprising, consisting of, or consisting essentially ofthe amino acid sequence RSSQSLLHSNGYNYLD (SEQ ID NO: 1),

(b) a VL CDR2 comprising, consisting of, or consisting essentially ofthe amino acid sequence LGSNRAS (SEQ ID NO: 2), and

(c) a VL CDR3 comprising, consisting of, or consisting essentially ofthe amino acid sequence MQALQTPLT (SEQ ID NO: 3), as shown in Table 1.

In some embodiments, the antibody comprises the VL framework regionsdescribed herein. In specific embodiments, the antibody comprises the VLframework regions (FRs) of an antibody set forth in Table 3.

In another embodiment, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises a heavy chain variableregion (VH) comprising:

(a) a VH CDR1 comprising, consisting of, or consisting essentially ofthe amino acid sequence GSAMH (SEQ ID NO: 4),

(b) a VH CDR2 comprising, consisting of, or consisting essentially ofthe amino acid sequence RIRSKANSYATAYAASVKG (SEQ ID NO: 5), and

(c) a VH CDR3 comprising, consisting of, or consisting essentially ofthe amino acid sequence GIYDSSGYDY (SEQ ID NO: 6), as shown in Table 2.

In some embodiments, the antibody comprises the VH frameworks describedherein. In specific embodiments, the antibody comprises the VH frameworkregions of an antibody set forth in Table 4.

TABLE 1 VL CDR Amino Acid Sequences ¹ Anti- VL CDR1 VL CDR2 VL CDR3 body(SEQ ID NO:) (SEQ ID NO:) (SEQ ID NO:) pab1949 RSSQSLLHSNGY LGSNRAS (2)MQALQTPLT NYLD (1) (3) ¹ The VL CDRs in Table 1 are determined accordingto Kabat.

TABLE 2 VH CDR Amino Acid Sequences ² Anti- VH CDR1 VH CDR2 VH CDR3 body(SEQ ID NO:) (SEQ ID NO:) (SEQ ID NO:) pab1949 GSAMH (4) RIRSKANSYATAGIYDSSGYDY YAASVKG (5) (6) ² The VH CDRs in Table 2 are determinedaccording to Kabat.

TABLE 3 VL FR Amino Acid Sequences ³ VL FR1 VL FR2 VL FR3 VL FR4 Anti-(SEQ ID (SEQ ID (SEQ ID (SEQ ID body NO:) NO:) NO:) NO:) pab1949DIVMTQSP WYLQKPG GVPDRFSG FGGGTKV LSLPVTPG QSPQLLI SGSGTDFT EIK (10)EPASISC (7) Y (8) LKISRVEA EDVGVYYC (9) ³ The VL framework regionsdescribed in Table 3 are determined based upon the boundaries of theKabat numbering system for CDRs. In other words, the VL CDRs aredetermined by Kabat and the framework regions are the amino acidresidues surrounding the CDRs in the variable region in the format FR1,CDR1, FR2, CDR2, FR3, CDR3, and FR4.

TABLE 4 VH FR Amino Acid Sequences ⁴ VH FRI VH FR2 VH FR3 VH FR4 Anti-(SEQ ID (SEQ ID (SEQ ID (SEQ ID body NO:) NO:) NO:) NO:) pab1949EVQLVESGG WVRQASG RFTISRDDSK WGQGTLVTV GLVQPGGSL KGLEWVG NTAYLQMNSLSS (14) KLSCAASGF (12) KTEDTAVYYC TFS (11) TS (13) ⁴ The VH frameworkregions described in Table 4 are determined based upon the boundaries ofthe Kabat numbering system for CDRs. In other words, the VH CDRs aredetermined by Kabat and the framework regions are the amino acidresidues surrounding the CDRs in the variable region in the format FR1,CDR1, FR2, CDR2, FR3, CDR3, and FR4.

In specific embodiments, the antibody comprises the four VL frameworkregions (FRs) set forth in Table 3 and the four VH framework regions(FRs) set forth in Table 4.

In certain embodiments, provided herein is an antibody whichspecifically binds to OX40 (e.g., human OX40) and comprises light chainvariable region (VL) CDRs and heavy chain variable region (VH) CDRs ofpab1949 or pab2044, for example as set forth in Tables 1 and 2 (i.e.,SEQ ID NOs: 1-6). In certain embodiments, provided herein is an antibodywhich specifically binds to OX40 (e.g., human OX40) and comprises lightchain variable region (VL) CDRs and heavy chain variable region (VH)CDRs of pab1949 or pab2044, for example as set forth in Tables 1 and 2(i.e., SEQ ID NOs: 1-6) and the VL framework regions and VH frameworkregions set forth in Tables 3 and 4.

In a particular embodiment, an antibody described herein, whichspecifically binds to OX40 (e.g., human OX40), comprises a light chainvariable region (VL) comprising VL CDR1, VL CDR2, and VL CDR3 as setforth in Table 1 and the VL framework regions of set forth in Table 3.

In certain embodiments, an antibody comprises a light chain variableframework region that is derived from an amino acid sequence encoded bya human gene, wherein the amino acid sequence is that of IGKV2-28*01(SEQ ID NO: 18).

In a particular embodiment, an antibody described herein, whichspecifically binds to OX40 (e.g., human OX40), comprises a heavy chainvariable region (VH) comprising VH CDR1, VH CDR2, and VH CDR3 as setforth in Table 2 and the VH framework regions set forth in Table 4.

In certain embodiments, the antibody comprises a heavy chain variableframework region that is derived from an amino acid sequence encoded bya human gene, wherein the amino acid sequence is that of IGHV3-73*01(SEQ ID NO: 19).

In a specific embodiment, an antibody that specifically binds to OX40(e.g., human OX40) comprises a VL domain comprising the amino acidsequence of SEQ ID NO: 15. In a specific embodiment, an antibody thatspecifically binds to OX40 (e.g., human OX40) comprises a VL domainconsisting of or consisting essentially of the amino acid sequence ofSEQ ID NO: 15.

In certain embodiments, an antibody that specifically binds to OX40(e.g., human OX40) comprises a VH domain comprising the amino acidsequence of SEQ ID NO: 16. In some embodiments, an antibody thatspecifically binds to OX40 (e.g., human OX40) comprises a VH domainconsisting of or consisting essentially of the amino acid sequence ofSEQ ID NO: 16.

In certain embodiments, an antibody that specifically binds to OX40(e.g., human OX40) comprises a VH domain and a VL domain, wherein the VHdomain and the VL domain comprise the amino acid sequences of SEQ ID NO:16 and SEQ ID NO: 15, respectively. In certain embodiments, an antibodythat specifically binds to OX40 (e.g., human OX40) comprises a VH domainand a VL domain, wherein the VH domain and the VL domain consist of orconsist essentially of the amino acid sequences of SEQ ID NO: 16 and SEQID NO: 15, respectively.

In certain aspects, an antibody described herein may be described by itsVL domain alone, or its VH domain alone, or by its 3 VL CDRs alone, orits 3 VH CDRs alone. See, for example, Rader C et al., (1998) PNAS 95:8910-8915, which is incorporated herein by reference in its entirety,describing the humanization of the mouse anti-αvβ3 antibody byidentifying a complementing light chain or heavy chain, respectively,from a human light chain or heavy chain library, resulting in humanizedantibody variants having affinities as high or higher than the affinityof the original antibody. See also Clackson T et al., (1991) Nature 352:624-628, which is incorporated herein by reference in its entirety,describing methods of producing antibodies that bind a specific antigenby using a specific VL domain (or VH domain) and screening a library forthe complementary variable domains. The screen produced 14 new partnersfor a specific VH domain and 13 new partners for a specific VL domain,which were strong binders, as determined by ELISA. See also Kim S J &Hong H J, (2007) J Microbiol 45: 572-577, which is incorporated hereinby reference in its entirety, describing methods of producing antibodiesthat bind a specific antigen by using a specific VH domain and screeninga library (e.g., human VL library) for complementary VL domains; theselected VL domains in turn could be used to guide selection ofadditional complementary (e.g., human) VH domains.

In certain aspects, the CDRs of an antibody can be determined accordingto the Chothia numbering scheme, which refers to the location ofimmunoglobulin structural loops (see, e.g., Chothia C & Lesk A M,(1987), J Mol Biol 196: 901-917; Al-Lazikani B et al., (1997) J Mol Biol273: 927-948; Chothia C et al., (1992) J Mol Biol 227: 799-817;Tramontano A et al., (1990) J Mol Biol 215(1): 175-82; and U.S. Pat. No.7,709,226). Typically, when using the Kabat numbering convention, theChothia CDR-H1 loop is present at heavy chain amino acids 26 to 32, 33,or 34, the Chothia CDR-H2 loop is present at heavy chain amino acids 52to 56, and the Chothia CDR-H3 loop is present at heavy chain amino acids95 to 102, while the Chothia CDR-L1 loop is present at light chain aminoacids 24 to 34, the Chothia CDR-L2 loop is present at light chain aminoacids 50 to 56, and the Chothia CDR-L3 loop is present at light chainamino acids 89 to 97. The end of the Chothia CDR-H1 loop when numberedusing the Kabat numbering convention varies between H32 and H34depending on the length of the loop (this is because the Kabat numberingscheme places the insertions at H35A and H35B; if neither 35A nor 35B ispresent, the loop ends at 32; if only 35A is present, the loop ends at33; if both 35A and 35B are present, the loop ends at 34).

In certain aspects, provided herein are antibodies that specificallybind to OX40 (e.g., human OX40) and comprise the Chothia VL CDRs of a VLof pab1949 or pab2044. In certain aspects, provided herein areantibodies that specifically bind to OX40 (e.g., human OX40) andcomprise the Chothia VH CDRs of a VH of pab1949 or pab2044. In certainaspects, provided herein are antibodies that specifically bind to OX40(e.g., human OX40) and comprise the Chothia VL CDRs of a VL of pab1949or pab2044 and comprise the Chothia VH CDRs of a VH of pab1949 orpab2044. In certain embodiments, antibodies that specifically bind toOX40 (e.g., human OX40) comprise one or more CDRs, in which the Chothiaand Kabat CDRs have the same amino acid sequence. In certainembodiments, provided herein are antibodies that specifically bind toOX40 (e.g., human OX40) and comprise combinations of Kabat CDRs andChothia CDRs.

In certain aspects, the CDRs of an antibody can be determined accordingto the IMGT numbering system as described in Lefranc M-P, (1999) TheImmunologist 7: 132-136 and Lefranc M-P et al., (1999) Nucleic Acids Res27: 209-212. According to the IMGT numbering scheme, VH-CDR1 is atpositions 26 to 35, VH-CDR2 is at positions 51 to 57, VH-CDR3 is atpositions 93 to 102, VL-CDR1 is at positions 27 to 32, VL-CDR2 is atpositions 50 to 52, and VL-CDR3 is at positions 89 to 97. In aparticular embodiment, provided herein are antibodies that specificallybind to OX40 (e.g., human OX40) and comprise CDRs of pab1949 or pab2044as determined by the IMGT numbering system, for example, as described inLefranc M-P (1999) supra and Lefranc M-P et al., (1999) supra).

In certain aspects, the CDRs of an antibody can be determined accordingto MacCallum R M et al., (1996) J Mol Biol 262: 732-745. See also, e.g.,Martin A. “Protein Sequence and Structure Analysis of Antibody VariableDomains,” in Antibody Engineering, Kontermann and Dübel, eds., Chapter31, pp. 422-439, Springer-Verlag, Berlin (2001). In a particularembodiment, provided herein are antibodies that specifically bind toOX40 (e.g., human OX40) and comprise CDRs of pab1949 or pab2044 asdetermined by the method in MacCallum R M et al.

In certain aspects, the CDRs of an antibody can be determined accordingto the AbM numbering scheme, which refers AbM hypervariable regionswhich represent a compromise between the Kabat CDRs and Chothiastructural loops, and are used by Oxford Molecular's AbM antibodymodeling software (Oxford Molecular Group, Inc.). In a particularembodiment, provided herein are antibodies that specifically bind toOX40 (e.g., human OX40) and comprise CDRs of pab1949 or pab2044 asdetermined by the AbM numbering scheme.

In a specific embodiment, the position of one or more CDRs along the VH(e.g., CDR1, CDR2, or CDR3) and/or VL (e.g., CDR1, CDR2, or CDR3) regionof an antibody described herein may vary by one, two, three, four, five,or six amino acid positions so long as immunospecific binding to OX40(e.g., human OX40) is maintained (e.g., substantially maintained, forexample, at least 50%, at least 60%, at least 70%, at least 80%, atleast 90%, at least 95%). For example, in one embodiment, the positiondefining a CDR of an antibody described herein can vary by shifting theN-terminal and/or C-terminal boundary of the CDR by one, two, three,four, five, or six amino acids, relative to the CDR position of anantibody described herein (e.g., pab1949 or pab2044), so long asimmunospecific binding to OX40 (e.g., human OX40) is maintained (e.g.,substantially maintained, for example, at least 50%, at least 60%, atleast 70%, at least 80%, at least 90%, at least 95%). In anotherembodiment, the length of one or more CDRs along the VH (e.g., CDR1,CDR2, or CDR3) and/or VL (e.g., CDR1, CDR2, or CDR3) region of anantibody described herein may vary (e.g., be shorter or longer) by one,two, three, four, five, or more amino acids, so long as immunospecificbinding to OX40 (e.g., human OX40) is maintained (e.g., substantiallymaintained, for example, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90%, at least 95%).

In one embodiment, a VL CDR1, VL CDR2, VL CDR3, VH CDR1, VH CDR2, and/orVH CDR3 described herein may be one, two, three, four, five or moreamino acids shorter than one or more of the CDRs described herein (e.g.,SEQ ID NO: 1-6) so long as immunospecific binding to OX40 (e.g., humanOX40) is maintained (e.g., substantially maintained, for example, atleast 50%, at least 60%, at least 70%, at least 80%, at least 90%, atleast 95%). In another embodiment, a VL CDR1, VL CDR2, VL CDR3, VH CDR1,VH CDR2, and/or VH CDR3 described herein may be one, two, three, four,five or more amino acids longer than one or more of the CDRs describedherein (e.g., SEQ ID NO: 1-6) so long as immunospecific binding to OX40(e.g., human OX40) is maintained (e.g., substantially maintained, forexample, at least 50%, at least 60%, at least 70%, at least 80%, atleast 90%, at least 95%). In another embodiment, the amino terminus of aVL CDR1, VL CDR2, VL CDR3, VH CDR1, VH CDR2, and/or VH CDR3 describedherein may be extended by one, two, three, four, five or more aminoacids compared to one or more of the CDRs described herein (e.g., SEQ IDNO: 1-6) so long as immunospecific binding to OX40 (e.g., human OX40) ismaintained (e.g., substantially maintained, for example, at least 50%,at least 60%, at least 70%, at least 80%, at least 90%, at least 95%).In another embodiment, the carboxy terminus of a VL CDR1, VL CDR2, VLCDR3, VH CDR1, VH CDR2, and/or VH CDR3 described herein may be extendedby one, two, three, four, five or more amino acids compared to one ormore of the CDRs described herein (e.g., SEQ ID NO: 1-6) so long asimmunospecific binding to OX40 (e.g., human OX40) is maintained (e.g.,substantially maintained, for example, at least 50%, at least 60%, atleast 70%, at least 80%, at least 90%, at least 95%). In anotherembodiment, the amino terminus of a VL CDR1, VL CDR2, VL CDR3, VH CDR1,VH CDR2, and/or VH CDR3 described herein may be shortened by one, two,three, four, five or more amino acids compared to one or more of theCDRs described herein (e.g., SEQ ID NO: 1-6) so long as immunospecificbinding to OX40 (e.g., human OX40) is maintained (e.g., substantiallymaintained, for example, at least 50%, at least 60%, at least 70%, atleast 80%, at least 90%, at least 95%). In one embodiment, the carboxyterminus of a VL CDR1, VL CDR2, VL CDR3, VH CDR1, VH CDR2, and/or VHCDR3 described herein may be shortened by one, two, three, four, five ormore amino acids compared to one or more of the CDRs described herein(e.g., SEQ ID NO: 1-6) so long as immunospecific binding to OX40 (e.g.,human OX40) is maintained (e.g., substantially maintained, for example,at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, atleast 95%). Any method known in the art can be used to ascertain whetherimmunospecific binding to OX40 (e.g., human OX40) is maintained, forexample, the binding assays and conditions described in the “Examples”section (Section 6) provided herein.

In specific aspects, provided herein is an antibody comprising anantibody light chain and heavy chain, e.g., a separate light chain andheavy chain. With respect to the light chain, in a specific embodiment,the light chain of an antibody described herein is a kappa light chain.In another specific embodiment, the light chain of an antibody describedherein is a lambda light chain. In yet another specific embodiment, thelight chain of an antibody described herein is a human kappa light chainor a human lambda light chain. In a particular embodiment, an antibodydescribed herein, which immunospecifically binds to an OX40 polypeptide(e.g., human OX40) comprises a light chain wherein the amino acidsequence of the VL domain comprises the sequence set forth in SEQ ID NO:15, and wherein the constant region of the light chain comprises theamino acid sequence of a human kappa light chain constant region. Inanother particular embodiment, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40) comprises a lightchain wherein the amino acid sequence of the VL domain comprises thesequence set forth in SEQ ID NO: 15 and wherein the constant region ofthe light chain comprises the amino acid sequence of a human lambdalight chain constant region. In a specific embodiment, an antibodydescribed herein, which immunospecifically binds to OX40 (e.g., humanOX40) comprises a light chain wherein the amino acid sequence of the VLdomain comprises the sequence set forth in SEQ ID NO: 15 and wherein theconstant region of the light chain comprises the amino acid sequence ofa human kappa or lambda light chain constant region. Non-limitingexamples of human constant region sequences have been described in theart, e.g., see U.S. Pat. No. 5,693,780 and Kabat E A et al., (1991)supra.

In a particular embodiment, an antibody described herein, whichspecifically binds to OX40 (e.g., human OX40) comprises a light chaincomprising the amino acid sequence set forth in SEQ ID NO: 20.

With respect to the heavy chain, in a specific embodiment, the heavychain of an antibody described herein can be an alpha (α), delta (δ),epsilon (ε), gamma (γ) or mu (μ) heavy chain. In another specificembodiment, the heavy chain of an antibody described can comprise ahuman alpha (α), delta (δ), epsilon (ε), gamma (γ) or mu (0 heavy chain.In a particular embodiment, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a heavychain wherein the amino acid sequence of the VH domain can comprise thesequence set forth in SEQ ID NO: 16 and wherein the constant region ofthe heavy chain comprises the amino acid sequence of a human gamma (γ)heavy chain constant region. In a specific embodiment, an antibodydescribed herein, which specifically binds to OX40 (e.g., human OX40),comprises a heavy chain wherein the amino acid sequence of the VH domaincomprises the sequence set forth in SEQ ID NO: 16, and wherein theconstant region of the heavy chain comprises the amino acid of a humanheavy chain described herein or known in the art. Non-limiting examplesof human constant region sequences have been described in the art, e.g.,see U.S. Pat. No. 5,693,780 and Kabat E A et al., (1991) supra.

In a particular embodiment, an antibody described herein, whichspecifically binds to OX40 (e.g., human OX40), comprises a heavy chaincomprising the amino acid sequence set forth in SEQ ID NO: 21. In aparticular embodiment, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises a heavy chain comprising theamino acid sequence set forth in SEQ ID NO: 60. In another embodiment,an antibody described herein, which specifically binds to OX40 (e.g.,human OX40), comprises a heavy chain comprising the amino acid sequenceset forth in SEQ ID NO: 23. In another embodiment, an antibody describedherein, which specifically binds to OX40 (e.g., human OX40), comprises aheavy chain comprising the amino acid sequence set forth in SEQ ID NO:61. In another embodiment, an antibody described herein, whichspecifically binds to OX40 (e.g., human OX40), comprises a heavy chaincomprising the amino acid sequence set forth in SEQ ID NO: 51. Inanother embodiment, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises a heavy chain comprising theamino acid sequence set forth in SEQ ID NO: 62. In another embodiment,an antibody described herein, which specifically binds to OX40 (e.g.,human OX40), comprises a heavy chain comprising the amino acid sequenceset forth in SEQ ID NO: 52. In another embodiment, an antibody describedherein, which specifically binds to OX40 (e.g., human OX40), comprises aheavy chain comprising the amino acid sequence set forth in SEQ ID NO:63.

In a specific embodiment, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40) comprises a VLdomain and a VH domain comprising any amino acid sequences describedherein, and wherein the constant regions comprise the amino acidsequences of the constant regions of an IgG, IgE, IgM, IgD, IgA, or IgYimmunoglobulin molecule, or a human IgG, IgE, IgM, IgD, IgA, or IgYimmunoglobulin molecule. In another specific embodiment, an antibodydescribed herein, which immunospecifically binds to OX40 (e.g., humanOX40) comprises a VL domain and a VH domain comprising any amino acidsequences described herein, and wherein the constant regions comprisethe amino acid sequences of the constant regions of an IgG, IgE, IgM,IgD, IgA, or IgY immunoglobulin molecule, any class (e.g., IgG₁, IgG₂,IgG₃, IgG₄, IgA₁, and IgA₂), or any subclass (e.g., IgG_(2a) andIgG_(2b)) of immunoglobulin molecule. In a particular embodiment, theconstant regions comprise the amino acid sequences of the constantregions of a human IgG, IgE, IgM, IgD, IgA, or IgY immunoglobulinmolecule, any class (e.g., IgG₁, IgG₂, IgG₃, IgG₄, IgA₁, and IgA₂), orany subclass (e.g., IgG₂a and IgG_(2b)) of immunoglobulin molecule.

In another specific embodiment, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VLdomain and a VH domain comprising any amino acid sequences describedherein, and wherein the constant regions comprise the amino acidsequences of the constant regions of a human IgG₁ (e.g., allotypes G1m3,G1m17,1 or G1m17,1,2), human IgG₂, or human IgG₄. In a particularembodiment, an antibody described herein, which immunospecifically bindsto OX40 (e.g., human OX40), comprises a VL domain and a VH domaincomprising any amino acid sequences described herein, and wherein theconstant regions comprise the amino acid sequences of the constantregion of a human IgG₁ (allotype Glm3). Non-limiting examples of humanconstant regions are described in the art, e.g., see Kabat E A et al.,(1991) supra.

In another embodiment, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises a light chain comprising theamino acid sequence set forth in SEQ ID NO: 20 and a heavy chaincomprising the amino acid sequence set forth in SEQ ID NO: 21. Inanother embodiment, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises a light chain comprising theamino acid sequence set forth in SEQ ID NO: 20 and a heavy chaincomprising the amino acid sequence set forth in SEQ ID NO: 60. Inanother embodiment, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises a light chain comprising theamino acid sequence set forth in SEQ ID NO: 20 and a heavy chaincomprising the amino acid sequence set forth in SEQ ID NO: 23. Inanother embodiment, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises a light chain comprising theamino acid sequence set forth in SEQ ID NO: 20 and a heavy chaincomprising the amino acid sequence set forth in SEQ ID NO: 61. Inanother embodiment, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises a light chain comprising theamino acid sequence set forth in SEQ ID NO: 20 and a heavy chaincomprising the amino acid sequence set forth in SEQ ID NO: 51 or 52. Inanother embodiment, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises a light chain comprising theamino acid sequence set forth in SEQ ID NO: 20 and a heavy chaincomprising the amino acid sequence set forth in SEQ ID NO: 62 or 63.

In certain embodiments, one, two, or more mutations (e.g., amino acidsubstitutions) are introduced into the Fc region of an antibodydescribed herein (e.g., CH2 domain (residues 231-340 of human IgG₁)and/or CH3 domain (residues 341-447 of human IgG₁) and/or the hingeregion, with numbering according to the Kabat numbering system (e.g.,the EU index in Kabat)) to alter one or more functional properties ofthe antibody, such as serum half-life, complement fixation, Fc receptorbinding and/or antigen-dependent cellular cytotoxicity.

In certain embodiments, one, two, or more mutations (e.g., amino acidsubstitutions) are introduced into the hinge region of the Fc region(CH1 domain) such that the number of cysteine residues in the hingeregion are altered (e.g., increased or decreased) as described in, e.g.,U.S. Pat. No. 5,677,425. The number of cysteine residues in the hingeregion of the CH1 domain may be altered to, e.g., facilitate assembly ofthe light and heavy chains, or to alter (e.g., increase or decrease) thestability of the antibody.

In some embodiments, one, two, or more mutations (e.g., amino acidsubstitutions) are introduced into the Fc region of an antibodydescribed herein (e.g., CH2 domain (residues 231-340 of human IgG₁)and/or CH3 domain (residues 341-447 of human IgG₁) and/or the hingeregion, with numbering according to the Kabat numbering system (e.g.,the EU index in Kabat)) to increase or decrease the affinity of theantibody for an Fc receptor (e.g., an activated Fc receptor) on thesurface of an effector cell. Mutations in the Fc region of an antibodythat decrease or increase the affinity of an antibody for an Fc receptorand techniques for introducing such mutations into the Fc receptor orfragment thereof are known to one of skill in the art. Examples ofmutations in the Fc receptor of an antibody that can be made to alterthe affinity of the antibody for an Fc receptor are described in, e.g.,Smith P et al., (2012) PNAS 109: 6181-6186, U.S. Pat. No. 6,737,056, andInternational Publication Nos. WO 02/060919; WO 98/23289; and WO97/34631, which are incorporated herein by reference.

In a specific embodiment, one, two, or more amino acid mutations (i.e.,substitutions, insertions or deletions) are introduced into an IgGconstant domain, or FcRn-binding fragment thereof (preferably an Fc orhinge-Fc domain fragment) to alter (e.g., decrease or increase)half-life of the antibody in vivo. See, e.g., International PublicationNos. WO 02/060919; WO 98/23289; and WO 97/34631; and U.S. Pat. Nos.5,869,046, 6,121,022, 6,277,375 and 6,165,745 for examples of mutationsthat will alter (e.g., decrease or increase) the half-life of anantibody in vivo. In some embodiments, one, two or more amino acidmutations (i.e., substitutions, insertions, or deletions) are introducedinto an IgG constant domain, or FcRn-binding fragment thereof(preferably an Fc or hinge-Fc domain fragment) to decrease the half-lifeof the antibody in vivo. In other embodiments, one, two or more aminoacid mutations (i.e., substitutions, insertions or deletions) areintroduced into an IgG constant domain, or FcRn-binding fragment thereof(preferably an Fc or hinge-Fc domain fragment) to increase the half-lifeof the antibody in vivo. In a specific embodiment, the antibodies mayhave one or more amino acid mutations (e.g., substitutions) in thesecond constant (CH2) domain (residues 231-340 of human IgG₁) and/or thethird constant (CH3) domain (residues 341-447 of human IgG₁), withnumbering according to the EU index in Kabat (Kabat E A et al., (1991)supra). In a specific embodiment, the constant region of the IgG₁ of anantibody described herein comprises a methionine (M) to tyrosine (Y)substitution in position 252, a serine (S) to threonine (T) substitutionin position 254, and a threonine (T) to glutamic acid (E) substitutionin position 256, numbered according to the EU index as in Kabat. SeeU.S. Pat. No. 7,658,921, which is incorporated herein by reference. Thistype of mutant IgG, referred to as “YTE mutant” has been shown todisplay fourfold increased half-life as compared to wild-type versionsof the same antibody (see Dall'Acqua W F et al., (2006) J Biol Chem 281:23514-24). In certain embodiments, an antibody comprises an IgG constantdomain comprising one, two, three or more amino acid substitutions ofamino acid residues at positions 251-257, 285-290, 308-314, 385-389, and428-436, numbered according to the EU index as in Kabat.

In a further embodiment, one, two, or more amino acid substitutions areintroduced into an IgG constant domain Fc region to alter the effectorfunction(s) of the antibody. For example, one or more amino acidsselected from amino acid residues 234, 235, 236, 237, 297, 318, 320 and322, numbered according to the EU index as in Kabat, can be replacedwith a different amino acid residue such that the antibody has analtered affinity for an effector ligand but retains the antigen-bindingability of the parent antibody. The effector ligand to which affinity isaltered can be, for example, an Fc receptor or the C1 component ofcomplement. This approach is described in further detail in U.S. Pat.Nos. 5,624,821 and 5,648,260. In some embodiments, the deletion orinactivation (through point mutations or other means) of a constantregion domain may reduce Fc receptor binding of the circulating antibodythereby increasing tumor localization. See, e.g., U.S. Pat. Nos.5,585,097 and 8,591,886 for a description of mutations that delete orinactivate the constant domain and thereby increase tumor localization.In certain embodiments, one or more amino acid substitutions may beintroduced into the Fc region of an antibody described herein to removepotential glycosylation sites on Fc region, which may reduce Fc receptorbinding (see, e.g., Shields R L et al., (2001) J Biol Chem 276:6591-604). In various embodiments, one or more of the followingmutations in the constant region of an antibody described herein may bemade: an N297A substitution; an N297Q substitution; a L235A substitutionand a L237A substitution; a L234A substitution and a L235A substitution;a E233P substitution; a L234V substitution; a L235A substitution; a C236deletion; a P238A substitution; a D265A substitution; a A327Qsubstitution; or a P329A substitution, numbered according to the EUindex as in Kabat. In certain embodiments, a mutation selected from thegroup consisting of D265A, P329A, and a combination thereof may be madein the constant region of an antibody described herein.

In a specific embodiment, an antibody described herein comprises theconstant domain of an IgG₁ with an N297Q or N297A amino acidsubstitution. In one embodiment, an antibody described herein comprisesthe constant domain of an IgG₁ with a mutation selected from the groupconsisting of D265A, P329A, and a combination thereof.

In certain embodiments, one or more amino acids selected from amino acidresidues 329, 331, and 322 in the constant region of an antibodydescribed herein, numbered according to the EU index as in Kabat, can bereplaced with a different amino acid residue such that the antibody hasaltered C1q binding and/or reduced or abolished complement dependentcytotoxicity (CDC). This approach is described in further detail in U.S.Pat. No. 6,194,551 (Idusogie et al). In some embodiments, one or moreamino acid residues within amino acid positions 231 to 238 in theN-terminal region of the CH2 domain of an antibody described herein arealtered to thereby alter the ability of the antibody to fix complement.This approach is described further in International Publication No. WO94/29351. In certain embodiments, the Fc region of an antibody describedherein is modified to increase the ability of the antibody to mediateantibody dependent cellular cytotoxicity (ADCC) and/or to increase theaffinity of the antibody for an Fcγ receptor by mutating one or moreamino acids (e.g., introducing amino acid substitutions) at thefollowing positions: 238, 239, 248, 249, 252, 254, 255, 256, 258, 265,267, 268, 269, 270, 272, 276, 278, 280, 283, 285, 286, 289, 290, 292,293, 294, 295, 296, 298, 301, 303, 305, 307, 309, 312, 315, 320, 322,324, 326, 327, 328, 329, 330, 331, 333, 334, 335, 337, 338, 340, 360,373, 376, 378, 382, 388, 389, 398, 414, 416, 419, 430, 434, 435, 437,438, or 439, numbered according to the EU index as in Kabat. Thisapproach is described further in International Publication No. WO00/42072.

In certain embodiments, an antibody described herein comprises theconstant domain of an IgG₁ with a mutation (e.g., substitution) atposition 267, 328, or a combination thereof, numbered according to theEU index as in Kabat. In certain embodiments, an antibody describedherein comprises the constant domain of an IgG₁ with a mutation (e.g.,substitution) selected from the group consisting of S267E, L328F, and acombination thereof. In certain embodiments, an antibody describedherein comprises the constant domain of an IgG₁ with a S267E/L328Fmutation (e.g., substitution). In certain embodiments, an antibodydescribed herein comprising the constant domain of an IgG₁ with aS267E/L328F mutation (e.g., substitution) has an increased bindingaffinity for FcγRIIA, FcγRIIB, or FcγRIIA and FcγRIIB

In certain embodiments, an antibody described herein comprises theconstant region of an IgG₄ antibody and the serine at amino acid residue228 of the heavy chain, numbered according to the EU index as in Kabat,is substituted for proline.

In certain embodiments, an antibody described herein comprises theconstant region of an IgG₂ antibody and the cysteine at amino acidresidue 127 of the heavy chain, numbered according to Kabat, issubstituted for serine.

Antibodies with reduced fucose content have been reported to have anincreased affinity for Fc receptors, such as, e.g., FcγRIIIAAccordingly, in certain embodiments, the antibodies described hereinhave reduced fucose content or no fucose content. Such antibodies can beproduced using techniques known to one skilled in the art. For example,the antibodies can be expressed in cells deficient or lacking theability of fucosylation. In a specific example, cell lines with aknockout of both alleles of α1,6-fucosyltransferase can be used toproduce antibodies with reduced fucose content. The Potelligent® system(Lonza) is an example of such a system that can be used to produceantibodies with reduced fucose content. Alternatively, antibodies withreduced fucose content or no fucose content can be produced by, e.g.:(i) culturing cells under conditions which prevent or reducefucosylation; (ii) posttranslational removal of fucose (e.g., with afucosidase enzyme); (iii) post-translational addition of the desiredcarbohydrate, e.g., after recombinant expression of a non-glycosylatedglycoprotein; or (iv) purification of the glycoprotein so as to selectfor antibodies thereof which are not fucsoylated. See, e.g., Longmore GD & Schachter H (1982) Carbohydr Res 100: 365-92 and Imai-Nishiya H etal., (2007) BMC Biotechnol. 7: 84 for methods for producing antibodiesthereof with no fucose content or reduced fucose content.

Engineered glycoforms may be useful for a variety of purposes, includingbut not limited to enhancing or reducing effector function. Methods forgenerating engineered glycoforms in an antibody described herein includebut are not limited to those disclosed, e.g., in Umaña P et al., (1999)Nat Biotechnol 17: 176-180; Davies J et al., (2001) Biotechnol Bioeng74: 288-294; Shields R L et al., (2002) J Biol Chem 277: 26733-26740;Shinkawa T et al., (2003) J Biol Chem 278: 3466-3473; Niwa R et al.,(2004) Clin Cancer Res 1: 6248-6255; Presta L G et al., (2002) BiochemSoc Trans 30: 487-490; Kanda Y et al., (2007) Glycobiology 17: 104-118;U.S. Pat. Nos. 6,602,684; 6,946,292; and 7,214,775; U.S. PatentPublication Nos. US 2007/0248600; 2007/0178551; 2008/0060092; and2006/0253928; International Publication Nos. WO 00/61739; WO 01/292246;WO 02/311140; and WO 02/30954; Potillegent™ technology (Biowa, Inc.Princeton, N.J.); and GlycoMAb® glycosylation engineering technology(Glycart biotechnology AG, Zurich, Switzerland). See also, e.g., FerraraC et al., (2006) Biotechnol Bioeng 93: 851-861; InternationalPublication Nos. WO 07/039818; WO 12/130831; WO 99/054342; WO 03/011878;and WO 04/065540.

In certain embodiments, the technology used to engineer the Fc domain ofan antibody described herein is the Xmab® Technology of Xencor(Monrovia, Calif.). See, e.g., U.S. Pat. Nos. 8,367,805; 8,039,592;8,124,731; 8,188,231; U.S. Patent Publication No. 2006/0235208;International Publication Nos. WO 05/077981; WO 11/097527; and RichardsJ O et al., (2008) Mol Cancer Ther 7: 2517-2527.

In certain embodiments, amino acid residues in the constant region of anantibody described herein in the positions corresponding to positionsL234, L235, and D265 in a human IgG1 heavy chain, numbered according tothe EU index of numbering, are not L, L, and D, respectively. Thisapproach is described in detail in International Publication No. WO14/108483. In a particular embodiment, the amino acids corresponding topositions L234, L235, and D265 in a human IgG1 heavy chain are F, E, andA; or A, A, and A, respectively.

In certain embodiments, any of the constant region mutations ormodifications described herein can be introduced into one or both heavychain constant regions of an antibody described herein having two heavychain constant regions.

In another particular embodiment, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a lightchain and a heavy chain, wherein (i) the light chain comprises a VLdomain comprising the VL CDR1, VL CDR2, and VL CDR3 amino acid sequencesset forth SEQ ID NOs: 1-3 (e.g., those listed in Table 1); (ii) theheavy chain comprises a VH domain comprising the VH CDR1, VH CDR2, andVH CDR3 amino acid sequences set forth in SEQ ID NOs: 4-6 (e.g., thoselisted in Table 2); (iii) the light chain further comprises a constantlight chain domain comprising the amino acid sequence of the constantdomain of a human kappa light chain; and (iv) the heavy chain furthercomprises a constant heavy chain domain comprising the amino acidsequence of the constant domain of a human IgG₁ (optionally IgG₁(allotype Glm3)) heavy chain.

In another particular embodiment, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a lightchain and a heavy chain, wherein (i) the light chain comprises a VLdomain comprising the amino acid set forth in SEQ ID NO: 15; (ii) theheavy chain comprises a VH domain comprising the amino acid sequence setforth in SEQ ID NO: 16; (iii) the light chain further comprises aconstant domain comprising the amino acid sequence of the constantdomain of a human kappa light chain; and (iv) the heavy chain furthercomprises a constant domain comprising the amino acid sequence of theconstant domain of a human IgG₁ (optionally IgG₁ (allotype Glm3)) heavychain.

In another particular embodiment, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a lightchain and a heavy chain, wherein (i) the light chain comprises a VLdomain comprising the VL CDR1, VL CDR2, and VL CDR3 amino acid sequencesset forth in SEQ ID NOs: 1-3 (e.g., those listed in Table 1); (ii) theheavy chain comprises a VH domain comprising the VH CDR1, VH CDR2, andVH CDR3 amino acid sequences set forth in SEQ ID NOs: 4-6 (e.g., thoselisted in Table 2); (iii) the light chain further comprises a constantlight chain domain comprising the amino acid sequence of the constantdomain of a human kappa light chain; and (iv) the heavy chain furthercomprises a constant heavy chain domain comprising the amino acidsequence of the constant domain of a human IgG₄ heavy chain.

In another particular embodiment, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a lightchain and a heavy chain, wherein (i) the light chain comprises a VLdomain comprising the amino acid sequence of SEQ ID NO: 15; (ii) theheavy chain comprises a VH domain comprising the amino acid sequence ofSEQ ID NO: 16; (iii) the light chain further comprises a constant domaincomprising the amino acid sequence of the constant domain of a humankappa light chain; and (iv) the heavy chain further comprises a constantdomain comprising the amino acid sequence of the constant domain of ahuman IgG₄ heavy chain.

In another particular embodiment, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a lightchain and a heavy chain, wherein (i) the light chain comprises a VLdomain comprising the VL CDR1, VL CDR2, and VL CDR3 amino acid sequencesset forth in SEQ ID NOs: 1-3 (e.g., those listed in Table 1); (ii) theheavy chain comprises a VH domain comprising the VH CDR1, VH CDR2, andVH CDR3 amino acid sequences set forth in SEQ ID NOs: 4-6 (e.g., thoselisted in Table 2); (iii) the light chain further comprises a constantlight chain domain comprising the amino acid sequence of the constantdomain of a human kappa light chain; and (iv) the heavy chain furthercomprises a constant heavy chain domain comprising the amino acidsequence of the constant domain of a human IgG₂ heavy chain.

In another particular embodiment, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a lightchain and a heavy chain, wherein (i) the light chain comprises a VLdomain comprising the amino acid sequence of SEQ ID NO: 15; (ii) theheavy chain comprises a VH domain comprising the amino acid sequence ofSEQ ID NO: 16; (iii) the light chain further comprises a constant domaincomprising the amino acid sequence of the constant domain of a humankappa light chain; and (iv) the heavy chain further comprises a constantdomain comprising the amino acid sequence of the constant domain of ahuman IgG₂ heavy chain. In certain embodiments, the light chaincomprises the amino acid sequence of SEQ ID NO: 50 and the heavy chaincomprises the amino acid sequence of SEQ ID NO: 51. In certainembodiments, the light chain comprises the amino acid sequence of SEQ IDNO: 50 and the heavy chain comprises the amino acid sequence of SEQ IDNO: 62. In certain embodiments, the light chain comprises the amino acidsequence of SEQ ID NO: 20 and the heavy chain comprises the amino acidsequence of SEQ ID NO: 51. In certain embodiments, the light chaincomprises the amino acid sequence of SEQ ID NO: 20 and the heavy chaincomprises the amino acid sequence of SEQ ID NO: 62.

In another specific embodiment, an antibody provided herein, whichspecifically binds to OX40 (e.g., human OX40), comprises (a) a heavychain comprising the amino acid sequence of SEQ ID NO: 21 with an aminoacid substitution of N to A or Q at amino acid position 297; and (b) alight chain comprising the amino acid sequence of SEQ ID NO: 20. Inanother specific embodiment, an antibody provided herein, whichspecifically binds to OX40 (e.g., human OX40), comprises (a) a heavychain comprising the amino acid sequence of SEQ ID NO: 60 with an aminoacid substitution of N to A or Q at amino acid position 297; and (b) alight chain comprising the amino acid sequence of SEQ ID NO: 20.

In another specific embodiment, an antibody provided herein, whichspecifically binds to OX40 (e.g., human OX40), comprises (a) a heavychain comprising the amino acid sequence of SEQ ID NO: 21 with an aminoacid substitution selected from the group consisting of: S to E at aminoacid position 267, L to F at amino acid position 328, and both S to E atamino acid position 267 and L to F at amino acid position 328; and (b) alight chain comprising the amino acid sequence of SEQ ID NO: 20. Inanother specific embodiment, an antibody provided herein, whichspecifically binds to OX40 (e.g., human OX40), comprises (a) a heavychain comprising the amino acid sequence of SEQ ID NO: 60 with an aminoacid substitution selected from the group consisting of: S to E at aminoacid position 267, L to F at amino acid position 328, and both S to E atamino acid position 267 and L to F at amino acid position 328; and (b) alight chain comprising the amino acid sequence of SEQ ID NO: 20.

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), exhibitsantibody-dependent cellular cytotoxicity (ADCC) activity. In specificembodiments, an antibody described herein, which immunospecificallybinds to OX40 (e.g., human OX40), initiates natural killer cell mediatedcell depletion. In specific embodiments, an antibody described herein,which immunospecifically binds to OX40 (e.g., human OX40), is used fortreating tumor infiltrated with natural killer cells. In specificembodiments, an antibody described herein, which immunospecificallybinds to OX40 (e.g., human OX40), exhibits antibody-dependent cellularphagocytosis (ADCP) activity. In specific embodiments, an antibodydescribed herein, which immunospecifically binds to OX40 (e.g., humanOX40), initiates macrophage mediated cell depletion. In specificembodiments, an antibody described herein, which immunospecificallybinds to OX40 (e.g., human OX40), is used for treating tumor infiltratedwith macrophages. In specific embodiments, an antibody described herein,which immunospecifically binds to OX40 (e.g., human OX40), selectivelydepletes intratumoral regulatory T cells.

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises frameworkregions (e.g., framework regions of the VL domain and/or VH domain) thatare human framework regions or derived from human framework regions.Non-limiting examples of human framework regions are described in theart, e.g., see Kabat E A et al., (1991) supra). In certain embodiment,an antibody described herein comprises framework regions (e.g.,framework regions of the VL domain and/or VH domain) that are primate(e.g., non-human primate) framework regions or derived from primate(e.g., non-human primate) framework regions.

For example, CDRs from antigen-specific non-human antibodies, typicallyof rodent origin (e.g., mouse or rat), are grafted onto homologous humanor non-human primate acceptor frameworks. In one embodiment, thenon-human primate acceptor frameworks are from Old World apes. In aspecific embodiment, the Old World ape acceptor framework is from Pantroglodytes, Pan paniscus or Gorilla gorilla. In a particularembodiment, the non-human primate acceptor frameworks are from thechimpanzee Pan troglodytes. In a particular embodiment, the non-humanprimate acceptor frameworks are Old World monkey acceptor frameworks. Ina specific embodiment, the Old World monkey acceptor frameworks are fromthe genus Macaca. In a certain embodiment, the non-human primateacceptor frameworks are is derived from the cynomolgus monkey Macacacynomolgus. Non-human primate framework sequences are described in U.S.Patent Application Publication No. US 2005/0208625.

In certain embodiments, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises one, two, or more VLframework regions (FRs) having the amino acid sequences described hereinfor the antibody set forth in Table 3, supra. In some embodiments, anantibody described herein, which specifically binds to OX40 (e.g., humanOX40), comprises one, two, or more VH framework regions (FRs) having theamino acid sequences described herein for the antibody set forth inTable 4, supra. In specific embodiments, an antibody described herein,which specifically binds to OX40 (e.g., human OX40), comprises one, two,or more VL framework regions having the amino acid sequences describedherein for the antibody set forth in Table 3, supra, and one, two, ormore VH framework regions having the amino acid sequences describedherein for the antibody set forth in Table 4, supra.

In some embodiments, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises one, two, three, or fourframework regions of the VL domain having the amino acid sequence ofpab1949 or pab2044 (e.g., SEQ ID NOs: 7-10) with 1, 2, 3, 4, 5, 6, 7, 8,9 or more amino acid mutations (e.g., amino acid substitutions, such asconservative amino acid substitutions) and/or the framework regions ofthe VH domain having the amino acid sequence of pab1949 or pab2044(e.g., SEQ ID NOs: 11-14). In certain embodiments, an antibody describedherein, which specifically binds to OX40 (e.g., human OX40), comprisesone, two, three, or four framework regions of the VH domain having theamino acid sequence of pab1949 or pab2044 (e.g., SEQ ID NOs: 11-14) with1, 2, 3, 4, 5, 6, 7, 8, 9 or more amino acid mutations (e.g., amino acidsubstitutions, such as conservative amino acid substitutions) and/or theframework regions of the VL domain having the amino acid sequence ofpab1949 or pab2044 (e.g., SEQ ID NOs: 7-10).

In certain embodiments, an antibody described herein, which specificallybinds to OX40 (e.g., human OX40), comprises VL framework regions (FRs)having at least 70%, at least 75%, at least 80%, at least 85%, at least90%, at least 95%, or at least 98% sequence identity to the VL frameworkregions described herein in Table 3, supra. In certain embodiments, anantibody described herein, which specifically binds to OX40 (e.g., humanOX40), comprises VH framework regions (FRs) having at least 70%, atleast 75%, at least 80%, at least 85%, at least 90%, at least 95%, or atleast 98% sequence identity to the VH framework regions described hereinTable 4, supra. In some embodiments, an antibody described herein, whichspecifically binds to OX40 (e.g., human OX40), comprises VH frameworkregions (FRs) having at least 70%, at least 75%, at least 80%, at least85%, at least 90%, at least 95%, or at least 98% sequence identity tothe VH framework regions described herein Table 4, supra, and VLframework regions (FRs) having at least 70%, at least 75%, at least 80%,at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the VL framework regions described herein Table 3, supra.

The determination of percent identity between two sequences (e.g., aminoacid sequences or nucleic acid sequences) can also be accomplished usinga mathematical algorithm. A specific, non-limiting example of amathematical algorithm utilized for the comparison of two sequences isthe algorithm of Karlin S & Altschul S F (1990) PNAS 87: 2264-2268,modified as in Karlin S & Altschul S F (1993) PNAS 90: 5873-5877. Suchan algorithm is incorporated into the NBLAST and XBLAST programs ofAltschul S F et al., (1990) J Mol Biol 215: 403. BLAST nucleotidesearches can be performed with the NBLAST nucleotide program parametersset, e.g., for score=100, wordlength=12 to obtain nucleotide sequenceshomologous to a nucleic acid molecules described herein. BLAST proteinsearches can be performed with the XBLAST program parameters set, e.g.,to score 50, wordlength=3 to obtain amino acid sequences homologous to aprotein molecule described herein. To obtain gapped alignments forcomparison purposes, Gapped BLAST can be utilized as described inAltschul S F et al., (1997) Nuc Acids Res 25: 3389 3402. Alternatively,PSI BLAST can be used to perform an iterated search which detectsdistant relationships between molecules (Id.). When utilizing BLAST,Gapped BLAST, and PSI Blast programs, the default parameters of therespective programs (e.g., of XBLAST and NBLAST) can be used (see, e.g.,National Center for Biotechnology Information (NCBI) on the worldwideweb, ncbi.nlm.nih.gov). Another specific, non-limiting example of amathematical algorithm utilized for the comparison of sequences is thealgorithm of Myers and Miller, 1988, CABIOS 4:11 17. Such an algorithmis incorporated in the ALIGN program (version 2.0) which is part of theGCG sequence alignment software package. When utilizing the ALIGNprogram for comparing amino acid sequences, a PAM120 weight residuetable, a gap length penalty of 12, and a gap penalty of 4 can be used.

The percent identity between two sequences can be determined usingtechniques similar to those described above, with or without allowinggaps. In calculating percent identity, typically only exact matches arecounted.

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15), wherein the antibody comprises VL CDRs that are identical to the VLCDRs of pab1949 or pab2044.

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VHdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VH domain of pab1949 or pab2044 (e.g., SEQ ID NO:16), wherein the antibody comprises VH CDRs that are identical to the VHCDRs of pab1949 or pab2044.

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises: (i) a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15); and (ii) a VH domain having at least 70%, at least 75%, at least80%, at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VH domain of pab1949 orpab2044 (e.g., SEQ ID NO: 16), wherein the antibody comprises VL CDRsand VH CDRs that are identical to the VL CDRs and VH CDRs of pab1949 orpab2044.

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15), wherein the antibody, in combination with StaphylococcusEnterotoxin A (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g.,PBMCs upon stimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and97% humidity, as measured by, e.g., electrochemiluminescence, e.g.,Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), whereinthe IL-2 production is a substantially increasing function of antibodyconcentrations between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. In certainembodiments, an antibody described herein, which immunospecificallybinds to OX40 (e.g., human OX40), comprises a VL domain having at least70%, at least 75%, at least 80%, at least 85%, at least 90%, at least95%, or at least 98% sequence identity to the amino acid sequence of theVL domain of pab1949 or pab2044 (e.g., SEQ ID NO: 15), wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA),induces IL-2 production in, e.g., PBMCs, wherein the IL-2 production isa substantially increasing function of antibody concentrations between,e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and 20 μg/ml, 0.8 μg/ml and20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and 4 μg/ml, 0.16 μg/ml and4 μg/ml, or 0.8 μg/ml and 4 μg/ml as assessed in, e.g., an assaycomprising the following steps: (a) culturing the PBMCs (e.g., 10⁵ cellsin a well) in the absence or presence of varying concentrations (e.g.,20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of theantibody and, e.g., 100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C.,5% CO₂, and 97% humidity; and (b) collecting clarified supernatant andmeasuring the titer of IL-2 by, e.g., electrochemiluminescence, e.g.,Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery).

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15), wherein the antibody, in combination with StaphylococcusEnterotoxin A (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g.,PBMCs upon stimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and97% humidity, as measured by, e.g., electrochemiluminescence, e.g.,Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), whereinthe IL-2 production shows a sigmoidal dose response curve when theanti-OX40 antibody is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16μg/ml and 20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032μg/ml and 4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. Incertain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15), wherein the antibody, in combination with StaphylococcusEnterotoxin A (SEA), induces IL-2 production in, e.g., PBMCs, whereinthe IL-2 production shows a sigmoidal dose response curve when theanti-OX40 antibody is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16μg/ml and 20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032μg/ml and 4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml asassessed in, e.g., an assay comprising the following steps: (a)culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery).

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VHdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VH domain of pab1949 or pab2044 (e.g., SEQ ID NO:16), wherein the antibody, in combination with StaphylococcusEnterotoxin A (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g.,PBMCs upon stimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and97% humidity, as measured by, e.g., electrochemiluminescence, e.g.,Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), whereinthe IL-2 production is a substantially increasing function of antibodyconcentrations between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. In certainembodiments, an antibody described herein, which immunospecificallybinds to OX40 (e.g., human OX40), comprises a VH domain having at least70%, at least 75%, at least 80%, at least 85%, at least 90%, at least95%, or at least 98% sequence identity to the amino acid sequence of theVH domain of pab1949 or pab2044 (e.g., SEQ ID NO: 16), wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA),induces IL-2 production in, e.g., PBMCs, wherein the IL-2 production isa substantially increasing function of antibody concentrations between,e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and 20 μg/ml, 0.8 μg/ml and20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and 4 μg/ml, 0.16 μg/ml and4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) culturing the PBMCs (e.g., 10⁵ cellsin a well) in the absence or presence of varying concentrations (e.g.,20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of theantibody and, e.g., 100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C.,5% CO₂, and 97% humidity; and (b) collecting clarified supernatant andmeasuring the titer of IL-2 by, e.g., electrochemiluminescence, e.g.,Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery).

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VHdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VH domain of pab1949 or pab2044 (e.g., SEQ ID NO:16), wherein the antibody, in combination with StaphylococcusEnterotoxin A (SEA) (e.g., 100 ng/ml), induces IL-2 production in, e.g.,PBMCs upon stimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and97% humidity, as measured by, e.g., electrochemiluminescence, e.g.,Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery), whereinthe IL-2 production shows a sigmoidal dose response curve when theanti-OX40 antibody is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16μg/ml and 20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032μg/ml and 4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. Incertain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VHdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VH domain of pab1949 or pab2044 (e.g., SEQ ID NO:16), wherein the antibody, in combination with StaphylococcusEnterotoxin A (SEA), induces IL-2 production in, e.g., PBMCs, whereinthe IL-2 production shows a sigmoidal dose response curve when theanti-OX40 antibody is between, e.g., 0.032 μg/ml and 20 μg/ml, 0.16μg/ml and 20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032μg/ml and 4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiter of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery).

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises: (i) a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15); and (ii) a VH domain having at least 70%, at least 75%, at least80%, at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VH domain of pab1949 orpab2044 (e.g., SEQ ID NO: 16), wherein the antibody, in combination withStaphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml), induces IL-2production in, e.g., PBMCs upon stimulation for, e.g., 5 days at, e.g.,37° C., 5% CO₂, and 97% humidity, as measured by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery), wherein the IL-2 production is a substantiallyincreasing function of antibody concentrations between, e.g., 0.032μg/ml and 20 μg/ml, 0.16 μg/ml and 20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4μg/ml and 20 μg/ml, 0.032 μg/ml and 4 μg/ml, 0.16 μg/ml and 4 μg/ml, or0.8 μg/ml and 4 μg/ml. In certain embodiments, an antibody describedherein, which immunospecifically binds to OX40 (e.g., human OX40),comprises: (i) a VL domain having at least 70%, at least 75%, at least80%, at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VL domain of pab1949 orpab2044 (e.g., SEQ ID NO: 15); and (ii) a VH domain having at least 70%,at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, orat least 98% sequence identity to the amino acid sequence of the VHdomain of pab1949 or pab2044 (e.g., SEQ ID NO: 16), wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA),induces IL-2 production in, e.g., PBMCs, wherein the IL-2 production isa substantially increasing function of antibody concentrations between,e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and 20 μg/ml, 0.8 μg/ml and20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and 4 μg/ml, 0.16 μg/ml and4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) culturing the PBMCs (e.g., 10⁵ cellsin a well) in the absence or presence of varying concentrations (e.g.,20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and 0.000256 μg/ml) of theantibody and, e.g., 100 ng/ml of SEA for, e.g., 5 days at, e.g., 37° C.,5% CO₂, and 97% humidity; and (b) collecting clarified supernatant andmeasuring the titer of IL-2 by, e.g., electrochemiluminescence, e.g.,Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery).

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises: (i) a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15); and (ii) a VH domain having at least 70%, at least 75%, at least80%, at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VH domain of pab1949 orpab2044 (e.g., SEQ ID NO: 16), wherein the antibody, in combination withStaphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml), induces IL-2production in, e.g., PBMCs upon stimulation for, e.g., 5 days at, e.g.,37° C., 5% CO₂, and 97% humidity, as measured by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery), wherein the IL-2 production shows a sigmoidaldose response curve when the anti-OX40 antibody is between, e.g., 0.032μg/ml and 20 μg/ml, 0.16 μg/ml and 20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4μg/ml and 20 μg/ml, 0.032 μg/ml and 4 μg/ml, 0.16 μg/ml and 4 μg/ml, or0.8 μg/ml and 4 μg/ml. In certain embodiments, an antibody describedherein, which immunospecifically binds to OX40 (e.g., human OX40),comprises: (i) a VL domain having at least 70%, at least 75%, at least80%, at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VL domain of pab1949 orpab2044 (e.g., SEQ ID NO: 15); and (ii) a VH domain having at least 70%,at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, orat least 98% sequence identity to the amino acid sequence of the VHdomain of pab1949 or pab2044 (e.g., SEQ ID NO: 16), wherein theantibody, in combination with Staphylococcus Enterotoxin A (SEA),induces IL-2 production in, e.g., PBMCs, wherein the IL-2 productionshows a sigmoidal dose response curve when the anti-OX40 antibody isbetween, e.g., 0.032 μg/ml and 20 μg/ml, 0.16 μg/ml and 20 μg/ml, 0.8μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and 4 μg/ml, 0.16μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, as assessed in, e.g., anassay comprising the following steps: (a) culturing the PBMCs (e.g., 10⁵cells in a well) in the absence or presence of varying concentrations(e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and 0.000256 μg/ml) ofthe antibody and, e.g., 100 ng/ml of SEA for, e.g., 5 days at, e.g., 37°C., 5% CO₂, and 97% humidity; and (b) collecting clarified supernatantand measuring the titer of IL-2 by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery).

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15), wherein the antibody when plate-bound, in combination with aplate-bound anti-CD3 antibody (e.g., 0.8 μg/ml), induces production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, in, e.g., PBMCs or T cells upon stimulation for, e.g., 4 days at,e.g., 37° C. and 5% CO₂, as measured by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery), whereinthe production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13, is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.7 μg/ml and 50 μg/ml,1.6 μg/ml and 50 μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs in the presence of a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml) and varying concentrations (e.g., 0, 0.3, 1,3, 6, 12, 25, and 50 μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50μg/ml) of the plate-bound antibody for, e.g., 4 days at, e.g., 37° C.and 5% CO₂; and (b) collecting supernatant and measuring the productionof one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10,or IL-13, by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery). In certain embodiments,an antibody described herein, which immunospecifically binds to OX40(e.g., human OX40), comprises a VL domain having at least 70%, at least75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least98% sequence identity to the amino acid sequence of the VL domain ofpab1949 or pab2044 (e.g., SEQ ID NO: 15), wherein the antibody whenplate-bound, in combination with a plate-bound anti-CD3 antibody (e.g.,0.8 μg/ml), induces production of one or more cytokines, e.g., TNFα,TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCs or T cellsupon stimulation for, e.g., 4 days at, e.g., 37° C. and 5% CO₂, asmeasured by, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plextissue culture kit (Meso Scale Discovery) or non-human primate (NHP)V-Plex assay kit (Meso Scale Discovery), wherein the production of oneor more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, shows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VHdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VH domain of pab1949 or pab2044 (e.g., SEQ ID NO:16), wherein the antibody when plate-bound, in combination with aplate-bound anti-CD3 antibody (e.g., 0.8 μg/ml), induces production ofone or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, in, e.g., PBMCs or T cells upon stimulation for, e.g., 4 days at,e.g., 37° C. and 5% CO₂, as measured by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery), whereinthe production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF,IL-2, IL-10, or IL-13, is a substantially increasing function of theconcentrations of the antibody between, e.g., 0.7 μg/ml and 50 μg/ml,1.6 μg/ml and 50 μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs in the presence of a plate-bound anti-CD3antibody (e.g., 0.8 μg/ml) and varying concentrations (e.g., 0, 0.3, 1,3, 6, 12, 25, and 50 μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50μg/ml) of the plate-bound antibody for, e.g., 4 days at, e.g., 37° C.and 5% CO₂; and (b) collecting supernatant and measuring the productionof one or more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10,or IL-13, by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery) or non-human primate(NHP) V-Plex assay kit (Meso Scale Discovery). In certain embodiments,an antibody described herein, which immunospecifically binds to OX40(e.g., human OX40), comprises a VH domain having at least 70%, at least75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least98% sequence identity to the amino acid sequence of the VH domain ofpab1949 or pab2044 (e.g., SEQ ID NO: 16), wherein the antibody whenplate-bound, in combination with a plate-bound anti-CD3 antibody (e.g.,0.8 μg/ml), induces production of one or more cytokines, e.g., TNFα,TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCs or T cellsupon stimulation for, e.g., 4 days at, e.g., 37° C. and 5% CO₂, asmeasured by, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plextissue culture kit (Meso Scale Discovery) or non-human primate (NHP)V-Plex assay kit (Meso Scale Discovery), wherein the production of oneor more cytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, orIL-13, shows a sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises: (i) a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15); and (ii) a VH domain having at least 70%, at least 75%, at least80%, at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VH domain of pab1949 orpab2044 (e.g., SEQ ID NO: 16), wherein the antibody when plate-bound, incombination with a plate-bound anti-CD3 antibody (e.g., 0.8 μg/ml),induces production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ,GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCs or T cells uponstimulation for, e.g., 4 days at, e.g., 37° C. and 5% CO₂, as measuredby, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery), wherein the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, is asubstantially increasing function of the concentrations of the antibodybetween, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50 μg/ml, 3.1 μg/mland 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) culturing the PBMCs in the presenceof a plate-bound anti-CD3 antibody (e.g., 0.8 μg/ml) and varyingconcentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50 μg/ml; or 0, 0.7,1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of the plate-bound antibody for,e.g., 4 days at, e.g., 37° C. and 5% CO₂; and (b) collecting supernatantand measuring the production of one or more cytokines, e.g., TNFα, TNFβ,IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery) ornon-human primate (NHP) V-Plex assay kit (Meso Scale Discovery). Incertain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises: (i) a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15); and (ii) a VH domain having at least 70%, at least 75%, at least80%, at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VH domain of pab1949 orpab2044 (e.g., SEQ ID NO: 16), wherein the antibody when plate-bound, incombination with a plate-bound anti-CD3 antibody (e.g., 0.8 μg/ml),induces production of one or more cytokines, e.g., TNFα, TNFβ, IFNγ,GM-CSF, IL-2, IL-10, or IL-13, in, e.g., PBMCs or T cells uponstimulation for, e.g., 4 days at, e.g., 37° C. and 5% CO₂, as measuredby, e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery), wherein the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, showsa sigmoidal dose response curve when the anti-OX40 antibodyconcentration is between, e.g., 0.7 μg/ml and 50 μg/ml, 1.6 μg/ml and 50μg/ml, 3.1 μg/ml and 50 μg/ml, or 6.3 μg/ml and 50 μg/ml, as assessedin, e.g., an assay comprising the following steps: (a) culturing thePBMCs in the presence of a plate-bound anti-CD3 antibody (e.g., 0.8μg/ml) and varying concentrations (e.g., 0, 0.3, 1, 3, 6, 12, 25, and 50μg/ml; or 0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) of theplate-bound antibody for, e.g., 4 days at, e.g., 37° C. and 5% CO₂; and(b) collecting supernatant and measuring the production of one or morecytokines, e.g., TNFα, TNFβ, IFNγ, GM-CSF, IL-2, IL-10, or IL-13, by,e.g., electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissueculture kit (Meso Scale Discovery) or non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15), wherein the antibody increases CD4+ T cell proliferation, whereinthe CD4+ T cell proliferation is a substantially increasing function ofthe concentrations of the antibody between, e.g., 0.2 μg/ml and 20μg/ml, or 2 μg/ml and 20 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry. In certain embodiments, an antibody describedherein, which immunospecifically binds to OX40 (e.g., human OX40),comprises a VL domain having at least 70%, at least 75%, at least 80%,at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VL domain of pab1949 orpab2044 (e.g., SEQ ID NO: 15), wherein the antibody results in a greaterincrease in CD4+ T cell proliferation when the antibody is present at aconcentration of 20 μg/ml than at a concentration of 2 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15), wherein the antibody increases CD4+ T cell proliferation, whereinthe CD4+ T cell proliferation shows a sigmoidal dose response curve whenthe anti-OX40 antibody concentration is between, e.g., 0.2 μg/ml and 20μg/ml, or 2 μg/ml and 20 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VHdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VH domain of pab1949 or pab2044 (e.g., SEQ ID NO:16), wherein the antibody increases CD4+ T cell proliferation, whereinthe CD4+ T cell proliferation is a substantially increasing function ofthe concentrations of the antibody between, e.g., 0.2 μg/ml and 20μg/ml, or 2 μg/ml and 20 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry. In certain embodiments, an antibody describedherein, which immunospecifically binds to OX40 (e.g., human OX40),comprises a VH domain having at least 70%, at least 75%, at least 80%,at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VH domain of pab1949 orpab2044 (e.g., SEQ ID NO: 16), wherein the antibody results in a greaterincrease in CD4+ T cell proliferation when the antibody is present at aconcentration of 20 μg/ml than at a concentration of 2 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a VHdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VH domain of pab1949 or pab2044 (e.g., SEQ ID NO:16), wherein the antibody increases CD4+ T cell proliferation, whereinthe CD4+ T cell proliferation shows a sigmoidal dose response curve whenthe anti-OX40 antibody concentration is between, e.g., 0.2 μg/ml and 20μg/ml, or 2 μg/ml and 20 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises: (i) a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15); and (ii) a VH domain having at least 70%, at least 75%, at least80%, at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VH domain of pab1949 orpab2044 (e.g., SEQ ID NO: 16), wherein the antibody increases CD4+ Tcell proliferation, wherein the CD4+ T cell proliferation is asubstantially increasing function of the concentrations of the antibodybetween, e.g., 0.2 μg/ml and 20 μg/ml, or 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In certain embodiments, an antibody described herein,which immunospecifically binds to OX40 (e.g., human OX40), comprises:(i) a VL domain having at least 70%, at least 75%, at least 80%, atleast 85%, at least 90%, at least 95%, or at least 98% sequence identityto the amino acid sequence of the VL domain of pab1949 or pab2044 (e.g.,SEQ ID NO: 15); and (ii) a VH domain having at least 70%, at least 75%,at least 80%, at least 85%, at least 90%, at least 95%, or at least 98%sequence identity to the amino acid sequence of the VH domain of pab1949or pab2044 (e.g., SEQ ID NO: 16), wherein the antibody results in agreater increase in CD4+ T cell proliferation when the antibody ispresent at a concentration of 20 μg/ml than at a concentration of 2μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises: (i) a VLdomain having at least 70%, at least 75%, at least 80%, at least 85%, atleast 90%, at least 95%, or at least 98% sequence identity to the aminoacid sequence of the VL domain of pab1949 or pab2044 (e.g., SEQ ID NO:15); and (ii) a VH domain having at least 70%, at least 75%, at least80%, at least 85%, at least 90%, at least 95%, or at least 98% sequenceidentity to the amino acid sequence of the VH domain of pab1949 orpab2044 (e.g., SEQ ID NO: 16), wherein the antibody increases CD4+ Tcell proliferation, wherein the CD4+ T cell proliferation shows asigmoidal dose response curve when the anti-OX40 antibody concentrationis between, e.g., 0.2 μg/ml and 20 μg/ml, or 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry.

In another aspect, provided herein are antibodies that bind the same oran overlapping epitope of OX40 (e.g., an epitope of human OX40) as anantibody described herein (e.g., pab1949 or pab2044). In certainembodiments, the epitope of an antibody can be determined by, e.g., NMRspectroscopy, X-ray diffraction crystallography studies, ELISA assays,hydrogen/deuterium exchange coupled with mass spectrometry (e.g., liquidchromatography electrospray mass spectrometry), array-basedoligo-peptide scanning assays, and/or mutagenesis mapping (e.g.,site-directed mutagenesis mapping). For X-ray crystallography,crystallization may be accomplished using any of the known methods inthe art (e.g., Giegé R et al., (1994) Acta Crystallogr D BiolCrystallogr 50(Pt 4): 339-350; McPherson A (1990) Eur J Biochem 189:1-23; Chayen N E (1997) Structure 5: 1269-1274; McPherson A (1976) JBiol Chem 251: 6300-6303). Antibody:antigen crystals may be studiedusing well known X-ray diffraction techniques and may be refined usingcomputer software such as X-PLOR (Yale University, 1992, distributed byMolecular Simulations, Inc.; see, e.g., Meth Enzymol (1985) volumes 114& 115, eds Wyckoff H W et al.; U.S. Patent Application No.2004/0014194), and BUSTER (Bricogne G (1993) Acta Crystallogr D BiolCrystallogr 49(Pt 1): 37-60; Bricogne G (1997) Meth Enzymol 276A:361-423, ed Carter C W; Roversi P et al., (2000) Acta Crystallogr D BiolCrystallogr 56(Pt 10): 1316-1323). Mutagenesis mapping studies may beaccomplished using any method known to one of skill in the art. See,e.g., Champe M et al., (1995) supra and Cunningham B C & Wells J A(1989) supra for a description of mutagenesis techniques, includingalanine scanning mutagenesis techniques. In a specific embodiment, theepitope of an antibody is determined using alanine scanning mutagenesisstudies. In addition, antibodies that recognize and bind to the same oroverlapping epitopes of OX40 (e.g., human OX40) can be identified usingroutine techniques such as an immunoassay, for example, by showing theability of one antibody to block the binding of another antibody to atarget antigen, i.e., a competitive binding assay. Competition bindingassays also can be used to determine whether two antibodies have similarbinding specificity for an epitope. Competitive binding can bedetermined in an assay in which the immunoglobulin under test inhibitsspecific binding of a reference antibody to a common antigen, such asOX40. Numerous types of competitive binding assays are known, forexample: solid phase direct or indirect radioimmunoassay (RIA), solidphase direct or indirect enzyme immunoassay (EIA), sandwich competitionassay (see Stahli C et al., (1983) Methods Enzymol 9: 242-253); solidphase direct biotin-avidin EIA (see Kirkland T N et al., (1986) JImmunol 137: 3614-9); solid phase direct labeled assay, solid phasedirect labeled sandwich assay (see Harlow E & Lane D, (1988) Antibodies:A Laboratory Manual, Cold Spring Harbor Press); solid phase direct labelRIA using I-125 label (see Morel G A et al., (1988) Mol Immunol 25(1):7-15); solid phase direct biotin-avidin EIA (Cheung R C et al., (1990)Virology 176: 546-52); and direct labeled RIA. (Moldenhauer G et al.,(1990) Scand J Immunol 32: 77-82). Typically, such an assay involves theuse of purified antigen (e.g., OX40 such as human OX40) bound to a solidsurface or cells bearing either of these, an unlabeled testimmunoglobulin and a labeled reference immunoglobulin. Competitiveinhibition can be measured by determining the amount of label bound tothe solid surface or cells in the presence of the test immunoglobulin.Usually the test immunoglobulin is present in excess. Usually, when acompeting antibody is present in excess, it will inhibit specificbinding of a reference antibody to a common antigen by at least 50-55%,55-60%, 60-65%, 65-70%, 70-75% or more. A competition binding assay canbe configured in a large number of different formats using eitherlabeled antigen or labeled antibody. In a common version of this assay,the antigen is immobilized on a 96-well plate. The ability of unlabeledantibodies to block the binding of labeled antibodies to the antigen isthen measured using radioactive or enzyme labels. For further detailssee, for example, Wagener C et al., (1983) J Immunol 130: 2308-2315;Wagener C et al., (1984) J Immunol Methods 68: 269-274; Kuroki M et al.,(1990) Cancer Res 50: 4872-4879; Kuroki M et al., (1992) Immunol Invest21: 523-538; Kuroki M et al., (1992) Hybridoma 11: 391-407 andAntibodies: A Laboratory Manual, Ed Harlow E & Lane D editors supra, pp.386-389.

In one embodiment, a competition assay is performed using surfaceplasmon resonance (BIAcore®), e.g., by an ‘in tandem approach’ such asthat described by Abdiche Y N et al., (2009) Analytical Biochem 386:172-180, whereby OX40 antigen is immobilized on the chip surface, forexample, a CMS sensor chip and the anti-OX40 antibodies are then runover the chip. To determine if an antibody competes with an anti-OX40antibody described herein, the anti-OX40 antibody is first run over thechip surface to achieve saturation and then the potential, competingantibody is added. Binding of the competing antibody can then bedetermined and quantified relative to a non-competing control.

In certain aspects, competition binding assays can be used to determinewhether an antibody is competitively blocked, e.g., in a dose dependentmanner, by another antibody for example, an antibody binds essentiallythe same epitope, or overlapping epitopes, as a reference antibody, whenthe two antibodies recognize identical or sterically overlappingepitopes in competition binding assays such as competition ELISA assays,which can be configured in all number of different formats, using eitherlabeled antigen or labeled antibody. In a particular embodiment, anantibody can be tested in competition binding assays with an antibodydescribed herein (e.g., antibody pab1949 or pab2044), or a chimeric orFab antibody thereof, or an antibody comprising VH CDRs and VL CDRs ofan antibody described herein (e.g., pab1949 or pab2044).

In another aspect, provided herein are antibodies that compete (e.g., ina dose dependent manner) for binding to OX40 (e.g., human OX40) with anantibody described herein (e.g., pab1949 or pab2044), as determinedusing assays known to one of skill in the art or described herein (e.g.,ELISA competitive assays or surface plasmon resonance). In anotheraspect, provided herein are antibodies that competitively inhibit (e.g.,in a dose dependent manner) an antibody described herein (e.g., pab1949or pab2044) from binding to OX40 (e.g., human OX40), as determined usingassays known to one of skill in the art or described herein (e.g., ELISAcompetitive assays, or suspension array or surface plasmon resonanceassay). In particular embodiments, such competitively blocking antibodyactivates, induces, or enhances one or more OX40 activities. In specificaspects, provided herein is an antibody which competes (e.g., in a dosedependent manner) for specific binding to OX40 (e.g., human OX40), withan antibody comprising the amino acid sequences described herein (e.g.,VL and/or VH amino acid sequences of antibody pab1949 or pab2044), asdetermined using assays known to one of skill in the art or describedherein (e.g., ELISA competitive assays, or suspension array or surfaceplasmon resonance assay).

In certain embodiments, provided herein is an antibody that competeswith an antibody described herein for binding to OX40 (e.g., human OX40)to the same extent that the antibody described herein self-competes forbinding to OX40 (e.g., human OX40). In some embodiments, provided hereinis a first antibody that competes with an antibody described herein forbinding to OX40 (e.g., human OX40), wherein the first antibody competesfor binding in an assay comprising the following steps: (a) incubatingOX40-transfected cells with the first antibody in unlabeled form in acontainer; and (b) adding an antibody described herein in labeled formin the container and incubating the cells in the container; and (c)detecting the binding of the antibody described herein in labeled formto the cells. In certain embodiments, provided herein is a firstantibody that competes with an antibody described herein for binding toOX40 (e.g., human OX40), wherein the competition is exhibited as reducedbinding of the first antibody to OX40 by more than 80% (e.g., 85%, 90%,95%, or 98%, or between 80% to 85%, 80% to 90%, 85% to 90%, or 85% to95%).

In specific aspects, provided herein is an antibody which competes(e.g., in a dose dependent manner) for specific binding to OX40 (e.g.,human OX40), with an antibody comprising a VL domain having the aminoacid sequence set forth in SEQ ID NO: 15, and a VH domain having theamino acid sequence set for the in SEQ ID NO: 16.

In specific aspects, provided herein is an antibody which competes(e.g., in a dose dependent manner) for specific binding to OX40 (e.g.,human OX40), with an antibody comprising (i) a VL domain comprising a VLCDR1, VL CDR2, and VL CDR3 having the amino acid sequences of the VLCDRs listed in Table 1; and (ii) a VH domain comprising a VH CDR1, VHCDR2, and VH CDR3 having the amino acid sequences of the CDRs listed inTable 2.

In a specific embodiment, an antibody described herein is one that iscompetitively blocked (e.g., in a dose dependent manner) by an antibodycomprising a VL domain having the amino acid sequence set forth in SEQID NO: 15 and a VH domain having the amino acid sequence set forth inSEQ ID NO: 16 for specific binding to OX40 (e.g., human OX40).

In another specific embodiment, an antibody described herein is one thatis competitively blocked (e.g., in a dose dependent manner) by anantibody comprising (i) a VL domain comprising a VL CDR1, VL CDR2, andVL CDR3 having the amino acid sequences of the CDRs listed in Table 1;and (ii) a VH domain comprising a VH CDR1, VH CDR2, and VH CDR3 havingthe amino acid sequences of the CDRs listed in Table 2.

In specific aspects, provided herein is an antibody, whichimmunospecifically binds to the same epitope as that of pab1949 orpab2044 for specific binding to OX40 (e.g., human OX40). Assays known toone of skill in the art or described herein (e.g., X-raycrystallography, hydrogen/deuterium exchange coupled with massspectrometry (e.g., liquid chromatography electrospray massspectrometry), alanine scanning, ELISA assays, etc.) can be used todetermine if two antibodies bind to the same epitope.

In a specific embodiment, an antibody described hereinimmunospecifically binds to the same epitope as that bound by pab1949 orpab2044 or an epitope that overlaps the epitope.

In another specific embodiment, an antibody described herein,immunospecifically binds to the same epitope as that of an antibodycomprising (i) a VL domain comprising a VL CDR1, VL CDR2, and VL CDR3having the amino acid sequences of the CDRs listed in Table 1 and (ii) aVH domain comprising a VH CDR1, VH CDR2, and VH CDR3 having the aminoacid sequences of the CDRs listed in Table 2.

In a specific aspect, the binding between an antibody described hereinand a variant OX40 is substantially weakened relative to the bindingbetween the antibody and a human OX40 sequence of SEQ ID NO:55, andwherein the variant OX40 comprises the sequence of SEQ ID NO: 55 exceptfor an amino acid mutation (e.g., substitution) selected from the groupconsisting of: N60A, R62A, R80A, L88A, P93A, P99A, P115A, and acombination thereof. In some embodiments, the variant OX40 comprises thesequence of SEQ ID NO: 55 except for any one mutation selected from thegroup consisting of: N60A, R62A, R80A, L88A, P93A, P99A, and P115A. Insome embodiments, the variant OX40 comprises the sequence of SEQ ID NO:55 except for any two, three, four, five, six, or seven mutationsselected from the group consisting of: W58A, N60A, R62A, R80A, L88A,P93A, P99A, and P115A. In some embodiments, the variant OX40 comprisesthe sequence of SEQ ID NO: 55 except for the amino acid mutations W58A,N60A, R62A, R80A, L88A, P93A, P99A, and P115A.

In a specific aspect, an antibody described herein specifically binds toan epitope of a human OX40 sequence comprising, consisting essentiallyof, or consisting of a residue of SEQ ID NO: 55 selected from the groupconsisting of: 60, 62, 80, 88, 93, 99, 115, and a combination thereof.In some embodiments, the epitope comprises, consists essentially of, orconsists of any one residue selected from the group consisting of: 60,62, 80, 88, 93, 99, and 115 of SEQ ID NO: 55. In some embodiments, theepitope comprises, consists essentially of, or consists of any two,three, four, five, six, or seven residues selected from the groupconsisting of: 58, 60, 62, 80, 88, 93, 99, and 115 of SEQ ID NO: 55. Insome embodiments, the epitope comprises, consists essentially of, orconsists of residues 58, 60, 62, 80, 88, 93, 99, and 115 of SEQ ID NO:55.

In a specific embodiment, an antibody described herein specificallybinds to an epitope of SEQ ID NO: 55 comprising, consisting essentiallyof, or consisting of a residue selected from the group consisting of:60, 62, 80, 88, 93, 99, 115, and a combination thereof. In someembodiments, the epitope comprises, consists essentially of, or consistsof any one residue selected from the group consisting of: 60, 62, 80,88, 93, 99, and 115 of SEQ ID NO: 55. In some embodiments, the epitopecomprises, consists essentially of, or consists of any two, three, four,five, six, or seven residues selected from the group consisting of: 58,60, 62, 80, 88, 93, 99, and 115 of SEQ ID NO: 55. In some embodiments,the epitope comprises, consists essentially of, or consists of residues58, 60, 62, 80, 88, 93, 99, and 115 of SEQ ID NO: 55.

In a specific aspect, an antibody described herein specifically binds toat least one residue of SEQ ID NO: 55 selected from the group consistingof: 60, 62, 80, 88, 93, 99, 115, and a combination thereof. In someembodiments, an antibody described herein specifically binds to any oneresidue, or any two, three, four, five, six, or seven residues, selectedfrom the group consisting of: 60, 62, 80, 88, 93, 99, and 115 of SEQ IDNO: 55. In some embodiments, an antibody described herein specificallybinds to any two, three, four, five, six, or seven residues selectedfrom the group consisting of: 58, 60, 62, 80, 88, 93, 99, and 115 of SEQID NO: 55. In some embodiments, an antibody described hereinspecifically binds to residues 58, 60, 62, 80, 88, 93, 99, 115 of SEQ IDNO: 55.

In a specific aspect, an antibody described herein exhibits, as comparedto binding to a human OX40 sequence of SEQ ID NO: 55, reduced or absentbinding to a protein identical to SEQ ID NO: 55 except for the presenceof an amino acid mutation (e.g., substitution) selected from the groupconsisting of: N60A, R62A, R80A, L88A, P93A, P99A, P115A, and acombination thereof. In some embodiments, the protein is identical toSEQ ID NO: 55 except for the presence of an amino acid mutationcomprising any one mutation, or any two, three, four, five, six, orseven mutations, selected from the group consisting of: N60A, R62A,R80A, L88A, P93A, P99A, and P115A. In some embodiments, the protein isidentical to SEQ ID NO: 55 except for the presence of an amino acidmutation comprising any two, three, four, five, six, or seven mutationsselected from the group consisting of: W58A, N60A, R62A, R80A, L88A,P93A, P99A, and P115A. In some embodiments, the protein is identical toSEQ ID NO: 55 except for the presence of an amino acid substitutioncomprising the mutations W58A, N60A, R62A, R80A, L88A, P93A, P99A, andP115A.

In certain embodiments, the epitope of an antibody described herein isused as an immunogen to produce antibodies. See, e.g., Section 5.3 infrafor methods for producing antibodies.

In specific aspects, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), functions as anagonist.

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), increases OX40(e.g., human OX40) activity by at least about 1.2 fold, 1.3 fold, 1.4fold, 1.5 fold, 2 fold, 2.5 fold, 3 fold, 3.5 fold, 4 fold, 4.5 fold, 5fold, 6 fold, 7 fold, 8 fold, 9 fold, 10 fold, 15 fold, 20 fold, 30fold, 40 fold, 50 fold, 60 fold, 70 fold, 80 fold, 90 fold, or 100 foldas assessed by methods described herein and/or known to one of skill inthe art, relative to OX40 (e.g., human OX40) activity without anyantibody or with an unrelated antibody (e.g., an antibody that does notimmunospecifically bind to OX40). In certain embodiments, an antibodydescribed herein, which immunospecifically binds to OX40 (e.g., humanOX40), increases OX40 (e.g., human OX40) activity by at least 5%, 10%,15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%,85%, 90%, 95%, 98%, or 99% as assessed by methods described hereinand/or known to one of skill in the art, relative to OX40 (e.g., humanOX40) activity without any antibody or with an unrelated antibody (e.g.,an antibody that does not immunospecifically bind to OX40). Non-limitingexamples of OX40 (e.g., human OX40) activity can include OX40 (e.g.,human OX40) signaling, cell proliferation, cell survival, and cytokineproduction (e.g., IL-2, TNF-α, IFN-γ, IL-4, IL-10, and/or IL-13). Incertain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), induces, enhances,or increases an OX40 (e.g., human OX40) activity. In specificembodiments, an increase in an OX40 activity is assessed as described inthe Examples, infra.

In certain aspects, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), induces, enhances,or increases the cellular proliferation of cells that express OX40 andthat respond to OX40 signaling (e.g., cells that proliferate in responseto OX40 stimulation and OX40 signaling, such as T cells). Cellproliferation assays are described in the art, such as a ³H-thymidineincorporation assay, BrdU incorporation assay, or CFSE assay, such asdescribed in Example 2, and can be readily carried out by one of skillin the art. In specific embodiments, T cells (e.g., CD4⁺ or CD8⁺effector T cells) stimulated with a T cell mitogen or T cell receptorcomplex stimulating agent (e.g., phytohaemagglutinin (PHA) and/orphorbol myristate acetate (PMA), or a TCR complex stimulating antibody,such as an anti-CD3 antibody and anti-CD28 antibody), in the presence ofan antibody described herein, which immunospecifically binds to OX40(e.g., human OX40), have increased cellular proliferation relative to Tcells only stimulated with the T cell mitogen or T cell receptor complexstimulating agent, such as phytohaemagglutinin (PHA) and/or phorbolmyristate acetate (PMA), or a TCR complex stimulating antibody, such asan anti-CD3 antibody and anti-CD28 antibody.

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), increases cellproliferation (e.g., T cells, such as CD4 and CD8 effector T cells) byat least about 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold, 2.5 fold,3 fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9fold, 10 fold, 15 fold, 20 fold, 30 fold, 40 fold, 50 fold, 60 fold, 70fold, 80 fold, 90 fold, or 100 fold, as assessed by methods describedherein or known to one of skill in the art (e.g., ³H-thymidineincorporation assay, BrdU incorporation assay or CFSE assay, such asdescribed in Example 2, infra), relative to OX40 (e.g., human OX40)activity stimulation without any antibody or with an unrelated antibody(e.g., an antibody that does not immunospecifically bind to OX40). Inspecific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), increases cellproliferation (e.g., T cells, such as CD4 and CD8 effector T cells) byat least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%,60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99%, as assessed bymethods described herein or known to one of skill in the art (e.g.,³H-thymidine incorporation assay, BrdU incorporation assay, or CFSEassay, such as described in Example 2, infra), relative to OX40 (e.g.,human OX40) activity without any antibody or with an unrelated antibody(e.g., an antibody that does not immunospecifically bind to OX40). Inspecific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), increases CD4+ Tcell proliferation, wherein the CD4+ T cell proliferation is asubstantially increasing function of the concentrations of the antibodybetween, e.g., 0.2 μg/ml and 20 μg/ml, as assessed in, e.g., an assaycomprising the following steps: (a) labeling, e.g., enriched CD4+ Tcells with, e.g., 10 μM carboxyfluorescein diacetate sucinimidyl ester(CFSE) for, e.g., 7 minutes at, e.g., 37° C.; (b) after extensivewashes, stimulating the cells (e.g., 10⁵ cells in a well) with, e.g., 3μg/ml of, e.g., plate-bound anti-CD3 antibody and varying concentrations(e.g., 0.002, 0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibodydescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry. In specific embodiments, an antibody describedherein, which immunospecifically binds to OX40 (e.g., human OX40),increases CD4+ T cell proliferation, wherein the CD4+ T cellproliferation is a substantially increasing function of theconcentrations of the antibody between, e.g., 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In specific embodiments, an antibody describedherein, which immunospecifically binds to OX40 (e.g., human OX40),increases CD4+ T cell proliferation, wherein the CD4+ T cellproliferation shows a sigmoidal dose response curve when the anti-OX40antibody concentration is between, e.g., 0.2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In specific embodiments, an antibody describedherein, which immunospecifically binds to OX40 (e.g., human OX40),increases CD4+ T cell proliferation, wherein the CD4+ T cellproliferation shows a sigmoidal dose response curve when the anti-OX40antibody concentration is between, e.g., 2 μg/ml and 20 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)labeling, e.g., enriched CD4+ T cells with, e.g., 10 μMcarboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody describedherein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4, stainingcells with, e.g., an anti-CD4 antibody and examining CD4+ T cellproliferation by, e.g., measuring the percentage of CFSE low CD4+ cellsby flow cytometry. In specific embodiments, an antibody describedherein, which immunospecifically binds to OX40 (e.g., human OX40),results in a greater increase in CD4+ T cell proliferation when theantibody is present at a concentration of 20 μg/ml than at aconcentration of 2 μg/ml, as assessed in, e.g., an assay comprising thefollowing steps: (a) labeling, e.g., enriched CD4+ T cells with, e.g.,10 μM carboxyfluorescein diacetate sucinimidyl ester (CFSE) for, e.g., 7minutes at, e.g., 37° C.; (b) after extensive washes, stimulating thecells (e.g., 10⁵ cells in a well) with, e.g., 3 μg/ml of, e.g.,plate-bound anti-CD3 antibody and varying concentrations (e.g., 0.002,0.02, 0.2, 2, and 20 μg/ml) of, e.g., plate-bound antibody thereofdescribed herein at, e.g., 37° C. and 5% CO₂; and (c) on, e.g., day 4,staining cells with, e.g., an anti-CD4 antibody and examining CD4+ Tcell proliferation by, e.g., measuring the percentage of CFSE low CD4+cells by flow cytometry.

In some embodiments, T cells (e.g., CD4⁺ or CD8⁺ effector T cells)stimulated with a T cell mitogen (e.g., an anti-CD3 antibody or phorbolester) in the presence of an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), have increasedcellular proliferation by at least about 1.2 fold, 1.3 fold, 1.4 fold,1.5 fold, 2 fold, 2.5 fold, 3 fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold,6 fold, 7 fold, 8 fold, 9 fold, 10 fold, 15 fold, 20 fold, 30 fold, 40fold, 50 fold, 60 fold, 70 fold, 80 fold, 90 fold, or 100 fold relativeto T cells only stimulated with the T cell mitogen, as assessed bymethods described herein or known to one of skill in the art (e.g.,³H-thymidine incorporation assay, BrdU incorporation assay, or CFSEassay, such as described in Example 2, infra). In some embodiments, Tcells (e.g., CD4⁺ or CD8⁺ effector T cells) stimulated with a T cellmitogen or T cell receptor complex stimulating agent (e.g.,phytohaemagglutinin (PHA) and/or phorbol myristate acetate (PMA), or aTCR complex stimulating antibody, such as an anti-CD3 antibody andanti-CD28 antibody) in the presence of an antibody described herein,which immunospecifically binds to OX40 (e.g., human OX40), haveincreased cellular proliferation by at least about 5%, 10%, 15%, 20%,25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%,95%, 98%, or 99% relative to T cells only stimulated with the T cellmitogen or T cell receptor complex stimulating agent (e.g.,phytohaemagglutinin (PHA) and/or phorbol myristate acetate (PMA), or aTCR complex stimulating antibody, such as an anti-CD3 antibody andanti-CD28 antibody), as assessed by methods described herein or known toone of skill in the art (e.g., ³H-thymidine incorporation assay, BrdUincorporation assay, or CFSE assay, such as described in Example 2,infra). In a specific embodiment, cell proliferation is assessed asdescribed in Example 2, infra. In specific embodiments, 5 μg/ml of anOX40 antibody described herein increases proliferation of human CD4 Tcells treated with 3 μg/ml anti-CD3 antibody by at least 20%. Inspecific embodiments, 5 μg/ml of an OX40 antibody described hereinincreases proliferation of human CD4 T cells treated with 3 μg/mlanti-CD3 antibody by at least 30%. In specific embodiments, 5 μg/ml ofan OX40 antibody described herein increases proliferation of human CD4 Tcells treated with 3 μg/ml anti-CD3 antibody by at least 40%. Inspecific embodiments, 5 μg/ml of an OX40 antibody described hereinincreases proliferation of human CD4 T cells treated with 3 μg/mlanti-CD3 antibody by at least 50%.

In certain aspects, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), increases thesurvival of cells (e.g., T cells, such as CD4 and CD8 effector T cells).In a specific embodiment, T cells (e.g., CD4⁺ or CD8⁺ effector T cells)stimulated with a T cell mitogen or T cell receptor complex stimulatingagent (e.g., phytohaemagglutinin (PHA) and/or phorbol myristate acetate(PMA), or a TCR complex stimulating antibody, such as an anti-CD3antibody and anti-CD28 antibody) in the presence of an antibodydescribed herein, which immunospecifically binds to OX40 (e.g., humanOX40), have increased survival relative to T cells only stimulated withthe T cell mitogen. Cell survival assays are described in the art (e.g.,a trypan blue exclusion assay) and can be readily carried out by one ofskill in the art.

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), increases cellsurvival (e.g., T cells, such as CD4 and CD8 effector T cells) by atleast about 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold, 2.5 fold, 3fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9fold, 10 fold, 15 fold, 20 fold, 30 fold, 40 fold, 50 fold, 60 fold, 70fold, 80 fold, 90 fold, or 100 fold, as assessed by methods describedherein or known to one of skill in the art (e.g., a trypan blueexclusion assay), without any antibody or with an unrelated antibody(e.g., an antibody that does not immunospecifically bind to OX40). Inspecific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), increases cellsurvival (e.g., T cells, such as CD4 and CD8 effector T cells) by atleast about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%,65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99%, as assessed by methodsdescribed herein or known to one of skill in the art (e.g., a trypanblue exclusion assay), relative to OX40 (e.g., human OX40) activitywithout any antibody or with an unrelated antibody (e.g., an antibodythat does not immunospecifically bind to OX40).

In some embodiments, T cells (e.g., CD4⁺ or CD8⁺ effector T cells)stimulated with a T cell mitogen (e.g., an anti-CD3 antibody or phorbolester) in the presence of an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), have increased cellsurvival by at least about 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2fold, 2.5 fold, 3 fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7fold, 8 fold, 9 fold, 10 fold, 15 fold, 20 fold, 30 fold, 40 fold, 50fold, 60 fold, 70 fold, 80 fold, 90 fold, or 100 fold relative to Tcells only stimulated with the T cell mitogen or T cell receptor complexstimulating agent (e.g., phytohaemagglutinin (PHA) and/or phorbolmyristate acetate (PMA), or a TCR complex stimulating antibody, such asan anti-CD3 antibody and anti-CD28 antibody), as assessed by methodsdescribed herein or known to one of skill in the art (e.g., a trypanblue exclusion assay). In some embodiments, T cells (e.g., CD4⁺ or CD8⁺effector T cells) stimulated with a T cell mitogen or T cell receptorcomplex stimulating agent (e.g., phytohaemagglutinin (PHA) and/orphorbol myristate acetate (PMA), or a TCR complex stimulating antibody,such as an anti-CD3 antibody and anti-CD28 antibody) in the presence ofan antibody described herein, which immunospecifically binds to OX40(e.g., human OX40), have increased cell survival by at least about 5%,10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, 98%, or 99% relative to T cells only stimulated withthe T cell mitogen, as assessed by methods described herein or known toone of skill in the art (e.g., a trypan blue exclusion assay).

In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), protects effector Tcells (e.g., CD4⁺ and CD8⁺ effector T cells) from activation-inducedcell death.

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), induces, enhances,or increases cytokine production (e.g., IL-2, TNF-α, IFN-γ, IL-4, IL-10,and/or IL-13) by at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%,45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99%, asassessed by methods described herein (see the Examples, infra, such asExample 2) or known to one of skill in the art, relative to cytokineproduction in the presence or absence of OX40L (e.g., human OX40L)stimulation without any antibody or with an unrelated antibody (e.g., anantibody that does not immunospecifically bind to OX40). In specificembodiments, an antibody described herein, which immunospecificallybinds to OX40 (e.g., human OX40), induces or enhances cytokineproduction (e.g., IL-2, TNF-α, IFN-γ, IL-4, IL-10, and/or IL-13) by atleast about 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold, 2.5 fold, 3fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9fold, 10 fold, 15 fold, 20 fold, 30 fold, 40 fold, 50 fold, 60 fold, 70fold, 80 fold, 90 fold, or 100 fold, as assessed by methods describedherein (see the Examples, infra, such as Example 2) or known to one ofskill in the art, relative to cytokine production in the presence orabsence of OX40L (e.g., human OX40L) stimulation without any antibody orwith an unrelated antibody (e.g., an antibody that does notimmunospecifically bind to OX40).

In certain embodiments, T cells (e.g., CD4⁺ or CD8⁺ effector T cells)stimulated with a T cell mitogen or T cell receptor complex stimulatingagent (e.g., phytohaemagglutinin (PHA) and/or phorbol myristate acetate(PMA), or a TCR complex stimulating antibody, such as an anti-CD3antibody and anti-CD28 antibody) in the presence of an antibodydescribed herein, which immunospecifically binds to OX40 (e.g., humanOX40), have increased cytokine production (e.g., IL-2, TNF-α, IFN-γ,IL-4, IL-10, and/or IL-13) by at least about 5%, 10%, 15%, 20%, 25%,30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%,98%, or 99% relative to T cells only stimulated with the T cell mitogenor T cell receptor complex stimulating agent (e.g., phytohaemagglutinin(PHA) and/or phorbol myristate acetate (PMA), or a TCR complexstimulating antibody, such as an anti-CD3 antibody and anti-CD28antibody), as assessed by methods described herein or known to one ofskill in the art (e.g., an ELISA assay or as described in the Examples,infra). In some embodiments, T cells (e.g., CD4⁺ or CD8⁺ effector Tcells) stimulated with a T cell mitogen or T cell receptor complexstimulating agent (e.g., phytohaemagglutinin (PHA) and/or phorbolmyristate acetate (PMA), or a TCR complex stimulating antibody, such asan anti-CD3 antibody and anti-CD28 antibody) in the presence of anantibody described herein, which immunospecifically binds to OX40 (e.g.,human OX40), have increased cytokine production (e.g., IL-2, TNF-α,IFN-γ, IL-4, IL-10, and/or IL-13) by at least about 1.2 fold, 1.3 fold,1.4 fold, 1.5 fold, 2 fold, 2.5 fold, 3 fold, 3.5 fold, 4 fold, 4.5fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, 10 fold, 15 fold, 20 fold,30 fold, 40 fold, 50 fold, 60 fold, 70 fold, 80 fold, 90 fold, or 100fold relative to T cells only stimulated with the T cell mitogen or Tcell receptor complex stimulating agent (e.g., phytohaemagglutinin (PHA)and/or phorbol myristate acetate (PMA), or a TCR complex stimulatingantibody, such as an anti-CD3 antibody and anti-CD28 antibody), asassessed by methods described herein or known to one of skill in the art(e.g., an ELISA assay or as described in the Examples, infra).

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), increases IL-2production in response to Staphylococcus Enterotoxin A (SEA) stimulationby at least about 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold, 2.5fold, 3 fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8fold, 9 fold, 10 fold, 15 fold, 20 fold, 30 fold, 40 fold, 50 fold, 60fold, 70 fold, 80 fold, 90 fold, or 100 fold, as assessed by methodsdescribed herein (see the Examples, infra, such as Example 2) or knownto one of skill in the art, relative to IL-2 production without anyantibody or with an unrelated antibody (e.g., an antibody that does notimmunospecifically bind to OX40).

In certain embodiments, T cells (e.g., CD4⁺ or CD8⁺ T cells) stimulatedwith Staphylococcus Enterotoxin A (SEA) stimulation in the presence ofan antibody described herein, which immunospecifically binds to OX40(e.g., human OX40), have increased IL-2 production by at least about 1.2fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold, 2.5 fold, 3 fold, 3.5 fold,4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, 10 fold, 15fold, 20 fold, 30 fold, 40 fold, 50 fold, 60 fold, 70 fold, 80 fold, 90fold, or 100 fold relative to T cells only stimulated with SEA, asassessed by methods described herein or known to one of skill in the art(e.g., an ELISA assay or as described in the Examples, infra).

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), in combination withStaphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml), induces IL-2production in, e.g., PBMCs upon stimulation for, e.g., 5 days at, e.g.,37° C., 5% CO₂, and 97% humidity, as measured by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery), wherein the IL-2 production is a substantiallyincreasing function of antibody concentrations between, e.g., 0.032μg/ml and 20 μg/ml. In certain embodiments, the IL-2 production inducedby the antibody in combination with SEA is a substantially increasingfunction of antibody concentrations between, e.g., 0.16 μg/ml and 20μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/ml and 4μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml. In anotherembodiment, an antibody described herein, which immunospecifically bindsto OX40 (e.g., human OX40), in combination with StaphylococcusEnterotoxin A (SEA), induces IL-2 production in, e.g., PBMCs, whereinthe IL-2 production is a substantially increasing function of antibodyconcentrations between, e.g., 0.032 μg/ml and 20 μg/ml, as assessed in,e.g., an assay comprising the following steps: (a) culturing the PBMCs(e.g., 10⁵ cells in a well) in the absence or presence of varyingconcentrations (e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and0.000256 μg/ml) of the antibody and, e.g., 100 ng/ml of SEA for, e.g., 5days at, e.g., 37° C., 5% CO₂, and 97% humidity; and (b) collectingclarified supernatant and measuring the titer of IL-2 by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery). In certain embodiments, an antibody describedherein, which immunospecifically binds to OX40 (e.g., human OX40), incombination with Staphylococcus Enterotoxin A (SEA), induces IL-2production in, e.g., PBMCs, wherein the IL-2 production is asubstantially increasing function of antibody concentrations between,e.g., 0.16 μg/ml and 20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20μg/ml, 0.032 μg/ml and 4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and4 μg/ml, as assessed in, e.g., an assay comprising the following steps:(a) culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiters of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery). In specificembodiments, an antibody described herein, which immunospecificallybinds to OX40 (e.g., human OX40), results in greater IL-2 production inresponse to Staphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml) uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, when the antibody is present at a concentration of 20 μg/mlthan at a concentration of 0.032 μg/ml. In a particular embodiment, anantibody described herein, which immunospecifically binds to OX40 (e.g.,human OX40), results in greater IL-2 production in response toStaphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml) upon stimulationfor, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97% humidity, when theantibody is present at a concentration of 20 μg/ml than at aconcentration of 0.16 μg/ml.

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), in combination withStaphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml), induces IL-2production in, e.g., PBMCs upon stimulation for, e.g., 5 days at, e.g.,37° C., 5% CO₂, and 97% humidity, as measured by, e.g.,electrochemiluminescence, e.g., Human TH1/TH2 10-Plex tissue culture kit(Meso Scale Discovery), wherein the IL-2 production shows a sigmoidaldose response curve when the anti-OX40 antibody concentration isbetween, e.g., 0.032 μg/ml and 20 μg/ml. In certain embodiments, theIL-2 production induced by the antibody in combination with SEA shows asigmoidal dose response curve when the anti-OX40 antibody concentrationis between, e.g., 0.16 μg/ml and 20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4μg/ml and 20 μg/ml, 0.032 μg/ml and 4 μg/ml, 0.16 μg/ml and 4 μg/ml, or0.8 μg/ml and 4 μg/ml. In another embodiment, an antibody describedherein, which immunospecifically binds to OX40 (e.g., human OX40), incombination with Staphylococcus Enterotoxin A (SEA), induces IL-2production in, e.g., PBMCs, wherein the IL-2 production shows asigmoidal dose response curve when the anti-OX40 antibody concentrationis between, e.g., 0.032 μg/ml and 20 μg/ml, as assessed in, e.g., anassay comprising the following steps: (a) culturing the PBMCs (e.g., 10⁵cells in a well) in the absence or presence of varying concentrations(e.g., 20, 4, 0.8, 0.16, 0.032, 0.0064, 0.00128, and 0.000256 μg/ml) ofthe antibody and, e.g., 100 ng/ml of SEA for, e.g., 5 days at, e.g., 37°C., 5% CO₂, and 97% humidity; and (b) collecting clarified supernatantand measuring the titer of IL-2 by, e.g., electrochemiluminescence,e.g., Human TH1/TH2 10-Plex tissue culture kit (Meso Scale Discovery).In certain embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), in combination withStaphylococcus Enterotoxin A (SEA), induces IL-2 production in, e.g.,PBMCs, wherein the IL-2 production shows a sigmoidal dose response curvewhen the anti-OX40 antibody concentration is between, e.g., 0.16 μg/mland 20 μg/ml, 0.8 μg/ml and 20 μg/ml, 4 μg/ml and 20 μg/ml, 0.032 μg/mland 4 μg/ml, 0.16 μg/ml and 4 μg/ml, or 0.8 μg/ml and 4 μg/ml, asassessed in, e.g., an assay comprising the following steps: (a)culturing the PBMCs (e.g., 10⁵ cells in a well) in the absence orpresence of varying concentrations (e.g., 20, 4, 0.8, 0.16, 0.032,0.0064, 0.00128, and 0.000256 μg/ml) of the antibody and, e.g., 100ng/ml of SEA for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity; and (b) collecting clarified supernatant and measuring thetiters of IL-2 by, e.g., electrochemiluminescence, e.g., Human TH1/TH210-Plex tissue culture kit (Meso Scale Discovery). In specificembodiments, an antibody described herein, which immunospecificallybinds to OX40 (e.g., human OX40), results in greater IL-2 production inresponse to Staphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml) uponstimulation for, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97%humidity, when the antibody is present at a concentration of 20 μg/mlthan at a concentration of 0.032 μg/ml. In a particular embodiment, anantibody described herein, which immunospecifically binds to OX40 (e.g.,human OX40), results in greater IL-2 production in response toStaphylococcus Enterotoxin A (SEA) (e.g., 100 ng/ml) upon stimulationfor, e.g., 5 days at, e.g., 37° C., 5% CO₂, and 97% humidity, when theantibody is present at a concentration of 20 μg/ml than at aconcentration of 0.16 μg/ml.

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), decreases IL-10production in response to Staphylococcus Enterotoxin A (SEA) stimulationby at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%, asassessed by methods described herein (see the Examples, infra, such asExample 2) or known to one of skill in the art, relative to IL-10production without any antibody or with an unrelated antibody (e.g., anantibody that does not immunospecifically bind to OX40).

In certain embodiments, T cells (e.g., CD4⁺ or CD8⁺ T cells) stimulatedwith Staphylococcus Enterotoxin A (SEA) stimulation in the presence ofan antibody described herein, which immunospecifically binds to OX40(e.g., human OX40), have decreased IL-10 production by at least about5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50% relative to T cellsonly stimulated with SEA, as assessed by methods described herein orknown to one of skill in the art (e.g., an ELISA assay or as describedin the Examples, infra).

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), when bound toactivated regulatory T cells, binds to activating Fc gamma receptorsselected from the group consisting of CD16, CD32A and CD64 to a greaterextent (e.g., 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold, 2.5 fold,3 fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9fold, 10 fold, 15 fold, 20 fold, 30 fold, 40 fold, 50 fold, 60 fold, 70fold, 80 fold, 90 fold, or 100 fold) than the antibody, when bound toactivated effector T cells, binds to the activating Fc gamma receptorsselected from the group consisting of CD16, CD32A and CD64, as assessedby methods described herein or known to one of skill in the art (e.g.,an Fc gamma receptor IIIA (CD16) reporter assay or as described in theExamples, infra). In specific embodiments, the activating Fc gammareceptors are expressed on a cell selected from the group consisting ofmyeloid-derived effector cells and lymphocyte-derived effector cells. Ina particular embodiment, the activating Fc gamma receptor is CD16.

In specific embodiments, an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), when bound toactivated regulatory T cells, causes stronger activation of activatingFc gamma receptors selected from the group consisting of CD16, CD32A andCD64 than the antibody, when bound to activated effector T cells, causesactivation of activating Fc gamma receptors selected from the groupconsisting of CD16, CD32A and CD64. In particular embodiments, theactivation of the activating Fc gamma receptors, when the antibodydescribed herein, which immunospecifically binds to OX40 (e.g., humanOX40), is bound to activated regulatory T cells, is at least about 1.2fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold, 2.5 fold, 3 fold, 3.5 fold,4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, 10 fold, 15fold, 20 fold, 30 fold, 40 fold, 50 fold, 60 fold, 70 fold, 80 fold, 90fold, or 100 fold stronger than the activation of the activating Fcgamma receptors, when the antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), is bound toactivated effector T cells, as assessed by methods described herein orknown to one of skill in the art (e.g., an Fc gamma receptor IIIA (CD16)reporter assay or as described in the Examples, infra). In specificembodiments, the activating Fc gamma receptors are expressed on a cellselected from the group consisting of myeloid-derived effector cells andlymphocyte-derived effector cells. In a particular embodiment, theactivating Fc gamma receptor is CD16.

In a specific aspect, provided herein are antagonist antibodies, whichimmunospecifically bind to OX40 (e.g., human OX40).

The activation of OX40 signaling depends on receptor clustering to formhigher order receptor complexes that efficiently recruit apical adapterproteins to drive intracellular signal transduction. Without being boundby theory, an anti-OX40 agonist antibody may mediate receptor clusteringthrough bivalent antibody arms (i.e., two antibody arms that each bindOX40 antigen) and/or through Fc-Fc receptor (FcR) co-engagement onaccessory myeloid or lymphoid cells. Consequently, one approach fordeveloping an anti-OX40 antagonist antibody is to select an antibodythat competes with OX40 ligand (OX40L) for binding to OX40, diminish oreliminate the binding of the Fc region of an antibody to Fc receptors,and/or adopt a monovalent antibody format. The monovalent antibodyformat can include antibodies that are structurally monovalent, such as,but not limited to, anti-OX40 antibodies comprising only oneantigen-binding domain (e.g., only one Fab arm), or antibodiescomprising only one antigen-binding domain that binds to OX40 (e.g.,human OX40) that is paired with a heavy chain or that is paired with afragment of a heavy chain (e.g., a Fc fragment). The monovalent antibodyformat can also include antibodies that are functionally monovalent, forexample, antibodies comprising only one antigen-binding domain thatbinds to OX40 (e.g., human OX40) that is paired with a second-antigenbinding domain that does not bind to an antigen expressed by a humanimmune cell (i.e., the antibody comprises two antigen-binding domains,but only one antigen-binding domain binds to OX40).

Examples of mutations of the IgG constant domain Fc region are discussedabove that can reduce Fc receptor binding or that can remove potentialglycosylation sites. In certain embodiments, the heavy chain constantregion of an antibody as described herein, which immunospecificallybinds to OX40 (e.g., human OX40), comprises a mutation selected from thegroup consisting of: N297A, N297Q, D265A, C127S, S228P, and acombination thereof. In certain embodiments, the mutation is N297A,N297Q, D265A, or a combination thereof. In certain embodiments, themutation is C127S. In certain embodiments, the mutation is S228P. In oneembodiment, the heavy chain constant region of an antibody as describedherein, which immunospecifically binds to OX40 (e.g., human OX40),comprises a mutation selected from the group consisting of D265A, P329A,and a combination thereof. In certain embodiments, the heavy chainconstant region is selected from the group consisting of immunoglobulinsIgG₁, IgG₂, IgG₃, IgG₄, IgA₁, and IgA₂. In certain embodiments, theimmunoglobulins are human immunoglobulins. Human immunoglobulinscontaining mutations (e.g., substitutions) are also referred to as humanimmunoglobulins herein. In a specific aspect, an antibody as describedherein, which immunospecifically binds to OX40 (e.g., human OX40),comprises a immunoglobulin IgG₁ heavy chain constant region, wherein theamino acid sequence of the IgG₁ heavy chain constant region comprises amutation selected from the group consisting of a N297A, N297Q, D265A, ora combination thereof. In one aspect, an antibody as described herein,which immunospecifically binds to OX40 (e.g., human OX40), comprises aimmunoglobulin IgG₁ heavy chain constant region, wherein the amino acidsequence of the IgG₁ heavy chain constant region comprises a mutationselected from the group consisting of D265A, P329A, and a combinationthereof. In a specific aspect, an antibody as described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises aimmunoglobulin IgG₂ heavy chain constant region, wherein the amino acidsequence of the IgG₂ heavy chain constant region comprises a C127Smutation. In a specific aspect, an antibody as described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), comprises aimmunoglobulin IgG₄ heavy chain constant region, wherein the amino acidsequence of the IgG₄ heavy chain constant region comprises a S228Pmutation. In certain embodiments, the antibody is antagonistic.

In a specific aspect, an antibody as described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), is selected fromthe group consisting of a Fab, Fab′, F(ab′)₂, and scFv fragment, whereinthe Fab, Fab′, F(ab′)₂, or scFv fragment comprises a heavy chainvariable region sequence and a light chain variable region sequence ofan anti-OX40 antigen-binding domain or antibody as described herein. AFab, Fab′, F(ab′)₂, or scFv fragment can be produced by any techniqueknown to those of skill in the art, including, but not limited to, thosediscussed in Section 5.3, infra. In certain embodiments, the Fab, Fab′,F(ab′)₂, or scFv fragment further comprises a moiety that extends thehalf-life of the antibody in vivo. The moiety is also termed a“half-life extending moiety.” Any moiety known to those of skill in theart for extending the half-life of a Fab, Fab′, F(ab′)₂, or scFvfragment in vivo can be used. For example, the half-life extendingmoiety can include a Fc region, a polymer, an albumin, or an albuminbinding protein or compound. The polymer can include a natural orsynthetic, optionally substituted straight or branched chainpolyalkylene, polyalkenylene, polyoxylalkylene, polysaccharide,polyethylene glycol, polypropylene glycol, polyvinyl alcohol,methoxypolyethylene glycol, lactose, amylose, dextran, glycogen, orderivative thereof. Substituents can include one or more hydroxy,methyl, or methoxy groups. In certain embodiments, the Fab, Fab′,F(ab′)₂, or scFv fragment can be modified by the addition of one or moreC-terminal amino acids for attachment of the half-life extending moiety.In certain embodiments the half-life extending moiety is polyethyleneglycol or human serum albumin. In certain embodiments, the Fab, Fab′,F(ab′)₂, or scFv fragment is fused to a Fc region. In certainembodiments, the antibody is antagonistic.

In a specific aspect, an antibody which immunospecifically binds to OX40(e.g., human OX40) comprises one heavy chain and one light chain (i.e.,the antibody does not comprise any additional heavy chain or light chainand comprises, consists essentially of, or consists of a single heavychain-light chain pair), wherein the heavy chain and light chaincomprise a heavy chain variable region sequence and a light chainvariable region sequence, respectively, of an anti-OX40 antigen-bindingdomain or antibody as described herein. In certain embodiments, theheavy chain comprises a mutation selected from the group consisting of:N297A, N297Q, D265A, C127S, S228P, and a combination thereof. In certainembodiments, the mutation is N297A, N297Q, D265A, or a combinationthereof. In certain embodiments, the mutation is C127S. In certainembodiments, the mutation is S228P. In certain embodiments, the heavychain comprises a mutation selected from the group consisting of D265A,P329A, and a combination thereof. In certain embodiments, the heavychain is selected from the group consisting of immunoglobulins IgG₁,IgG₂, IgG₃, IgG₄, IgA₁, and IgA₂. In certain embodiments, theimmunoglobulins are human immunoglobulins. In certain embodiments, theheavy chain is an IgG₁ heavy chain comprising a mutation selected fromthe group consisting of N297A, N297Q, D265A, or a combination thereof.In certain embodiments, the heavy chain is an IgG₂ heavy chaincomprising a C127S mutation. In certain embodiments, the heavy chain isan IgG₄ heavy chain comprising a S228P mutation. In certain embodiments,the heavy chain is an IgG₁ heavy chain comprising a mutation selectedfrom the group consisting of D265A, P329A and a combination thereof. Incertain embodiments, the antibody is antagonistic.

In a specific aspect, an antibody as described herein whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a firstantigen-binding domain that binds to OX40, as described herein; and asecond antigen-binding domain that does not specifically bind to anantigen expressed by a human immune cell (i.e., the secondantigen-binding domain does not bind to OX40 or any other antigenexpressed by a human immune cell), as described herein. In certainembodiments, the first and second antigen-binding domains comprisecomplementary CH3 domains. For example, the complementary CH3 domainsallow for heterodimerization to preferentially occur between the heavychain of the first antigen-binding domain and the heavy chain of thesecond antigen-binding domain rather than homodimerization of therespective antigen-binding domains. Any technique known to those ofskill in the art can be used to produce complementary CH3 domains,including, but not limited to, knob-into-hole technology as described inRidgway J B B et al., (1996) Protein Eng 9(7): 617-621 and Merchant M etal. For example, the knob-into-hole technology replaces a small aminoacid with a larger amino acid (i.e., the “knob”) in a first CH3 domainand replaces a large amino acid with a smaller amino acid (i.e., the“hole”) in a second CH3 domain. Polypeptides comprising the CH3 domainscan then dimerize based on interaction of the knob and hole. In certainembodiments, one of the antigen-binding domains comprises a first IgG₁CH3 domain comprising a substitution selected from the group consistingof T366Y and T366W, and the other antigen-binding domain comprises asecond IgG₁ CH3 domain comprising a substitution selected from the groupconsisting of Y407T, T366S, L368A, and Y407V. In certain embodiments,the antigen to which the second antigen-binding domain binds is notnaturally expressed by a human immune cell. In certain embodiments, theimmune cell is selected from the group consisting of a T cell (e.g., aCD4+ T cell or a CD8+ T cell), a B cell, a natural killer cell, adendritic cell, a macrophage, and an eosinophil. In certain embodiments,the antigen-binding domain that specifically binds to OX40 comprises afirst VH and a first VL, and the second antigen-binding domain comprisesa second VH and a second VL. In certain embodiments, the antigen-bindingdomain that specifically binds to OX40 comprises a first heavy chain anda first light chain, and the second antigen-binding domain comprises asecond heavy chain and a second light chain. In certain embodiments, theantibody is for administration to a sample or subject in which thesecond antigen-binding domain is non-reactive (i.e., the antigen towhich the second antigen-binding domain binds is not present in thesample or subject). In certain embodiments, the second antigen-bindingdomain does not specifically bind to an antigen on a cell expressingOX40 (e.g., the second antigen-binding domain does not bind to anantigen that is naturally expressed by a cell that expresses OX40). Incertain embodiments, the antibody functions as a monovalent antibody(i.e., an anti-OX40-monovalent antibody) in a sample or subject, whereinthe first antigen-binding domain of the antibody binds to OX40, whilethe second antigen-binding domain is non-reactive in the sample orsubject (e.g., due to the absence of antigen to which the secondantigen-binding domain binds in the sample or subject). In certainembodiments, the second antigen-binding domain specifically binds to anon-human antigen (i.e., an antigen expressed in other organisms and nothumans). In certain embodiments, the second antigen-binding domainspecifically binds to a viral antigen. In certain embodiments, the viralantigen is from a virus that does not infect humans (i.e., a non-humanvirus). In certain embodiments, the viral antigen is absent in a humanimmune cell (e.g., the human immune cell is uninfected with the virusassociated with the viral antigen). In certain embodiments, the viralantigen is a HIV antigen. In certain embodiments, the secondantigen-binding domain specifically binds to chicken albumin or hen egglysozyme. In certain embodiments, the second antigen-binding domainspecifically binds to an antigen that is not expressed by (i.e., isabsent from) wild-type cells (e.g., wild-type human cells). In certainembodiments, the second antigen-binding domain specifically binds to atumor-associated antigen that is not expressed by (i.e., is absent from)normal cells (e.g., wild-type cells, e.g., wild-type human cells). Incertain embodiments, the tumor-associated antigen is not expressed by(i.e., is absent from) human cells. In certain embodiments, the heavychain constant region of the second antigen-binding domain comprises amutation selected from the group consisting of: N297A, N297Q, D265A,C127S, S228P, and a combination thereof. In certain embodiments, themutation is N297A, N297Q, D265A, or a combination thereof. In certainembodiments, the mutation is C127S. In certain embodiments, the mutationis S228P. In certain embodiments, the heavy chain constant region of thesecond antigen-binding domain comprises a mutation selected from thegroup consisting of D265A, P329A, and a combination thereof. In certainembodiments, the heavy chain constant region of the first and secondantigen-binding domains is selected from the group consisting ofimmunoglobulins IgG₁, IgG₂, IgG₃, IgG₄, IgA₁, and IgA₂. In certainembodiments, the immunoglobulins are human immunoglobulins. In certainembodiments, the heavy chain constant regions of the first and secondantigen-binding domains are the same isotype. In certain embodiments,the first antigen-binding domain comprises a first IgG₁ heavy chainconstant region and the second antigen-binding domain comprises a secondIgG₁ heavy chain constant region, wherein the first and second heavychain constant regions comprise an identical mutation selected from thegroup consisting of N297A, N297Q, D265A, or a combination thereof. Incertain embodiments, the first antigen-binding domain comprises a firstIgG₁ heavy chain constant region and the second antigen-binding domaincomprises a second IgG₁ heavy chain constant region, wherein the firstand second heavy chain constant regions comprise an identical mutationselected from the group consisting of D265A, P329A, or a combinationthereof. In certain embodiments, the first antigen-binding domaincomprises a first IgG₂ heavy chain constant region and the secondantigen-binding domain comprises a second IgG₂ heavy chain constantregion, wherein the first and second heavy chain constant regionscomprise a C127S mutation. In certain embodiments, the firstantigen-binding domain comprises a first IgG₄ heavy chain constantregion and the second antigen-binding domain comprises a second IgG₄heavy chain constant region, wherein the first and second heavy chainconstant regions comprise a S228P mutation. In certain embodiments, theantibody is antagonistic.

In a specific aspect, an antibody as described herein whichimmunospecifically binds to OX40 (e.g., human OX40), comprises a firstantigen-binding domain that specifically binds to OX40, comprising afirst heavy chain and a first light chain; and a second heavy chain or afragment thereof. In certain embodiments, the first and second heavychain, or fragment of the second heavy chain, comprise complementary CH3domains. For example, the complementary CH3 domains allow forheterodimerization to preferentially occur between the heavy chainsrather than homodimerization of the respective heavy chains. In certainembodiments, one of the heavy chains comprises a first IgG₁ CH3 domaincomprising a substitution selected from the group consisting of T366Yand T366W, and the other heavy chain comprises a second IgG₁ CH3 domaincomprising a substitution selected from the group consisting of Y407T,T366S, L368A, Y407V. In some embodiments, the fragment of the secondheavy chain is a Fc fragment. In certain embodiments, the second heavychain or fragment thereof is from an antigen-binding domain thatspecifically binds to a non-human antigen (i.e., an antigen expressed inother organisms and not humans). In certain embodiments, the secondheavy chain or fragment thereof is from an antigen-binding domain thatspecifically binds to a viral antigen. In certain embodiments, the viralantigen is absent in a human immune cell (e.g., the human immune cell isuninfected with the virus associated with the viral antigen). In certainembodiments, the viral antigen is a HIV antigen. In certain embodiments,the second heavy chain or fragment thereof is from an antigen-bindingdomain that specifically binds to chicken albumin or hen egg lysozyme.In certain embodiments, the second heavy chain or fragment thereof isfrom an antigen-binding domain that specifically binds to an antigenthat is not expressed by (i.e., is absent from) wild-type cells (e.g.,wild-type human cells). In certain embodiments, the second heavy chainor fragment thereof is from an antigen-binding domain that specificallybinds to a tumor-associated antigen that is not expressed by (i.e., isabsent from) normal cells (e.g., wild-type cells, e.g., wild-type humancells). In certain embodiments, the tumor-associated antigen is notexpressed by (i.e., is absent from) human cells. In certain embodiments,the second heavy chain or fragment thereof comprises a mutation selectedfrom the group consisting of: N297A, N297Q, D265A, C127S, S228P, and acombination thereof. In certain embodiments, the mutation is N297A,N297Q, D265A, or a combination thereof. In certain embodiments, themutation is C127S. In certain embodiments, the mutation is S228P. Incertain embodiments, the second heavy chain or fragment thereofcomprises a mutation selected from the group consisting of D265A, P329A,and a combination thereof. In certain embodiments, the first and secondheavy chain constant regions are selected from the group consisting ofimmunoglobulins IgG₁, IgG₃, IgG₄, IgA₁, and IgA₂. In certainembodiments, the immunoglobulins are human immunoglobulins. In certainembodiments, the first and second heavy chain constant regions are thesame isotype. In certain embodiments, the first and second heavy chainconstant regions are IgG₁ constant regions and comprise an identicalmutation selected from the group consisting of N297A, N297Q, D265A, or acombination thereof. In certain embodiments, the first and second heavychain constant regions are IgG₁ constant regions and comprise anidentical mutation selected from the group consisting of D265A, P329A,and a combination thereof. In certain embodiments, the first and secondheavy chain constant regions are IgG₂ heavy chain constant regions andcomprise a C127S mutation. In certain embodiments, the first and secondheavy chain constant regions are IgG₄ heavy chain constant regions andcomprise a S228P mutation. In certain embodiments, the antibody isantagonistic.

In the above aspects directed to an antibody comprising anantigen-binding domain that specifically binds to OX40 (e.g., humanOX40) and either a second antigen-binding domain or a second heavy chainor fragment thereof, the antigen-binding domain can comprise any of theanti-OX40 sequences described herein. In certain embodiments, theantigen-binding domain that specifically binds to OX40 (e.g., humanOX40) comprises: (a) a first heavy chain variable domain (VH) comprisinga VH-complementarity determining region (CDR) 1 comprising the aminoacid sequence of GSAMH (SEQ ID NO:4); a VH-CDR2 comprising the aminoacid sequence of RIRSKANSYATAYAASVKG (SEQ ID NO:5); and a VH-CDR3comprising the amino acid sequence of GIYDSSGYDY (SEQ ID NO:6); and (b)a first light chain variable domain (VL) comprising a VL-CDR1 comprisingthe amino acid sequence of RSSQSLLHSNGYNYLD (SEQ ID NO:1); a VL-CDR2comprising the amino acid sequence of LGSNRAS (SEQ ID NO:2); and aVL-CDR3 comprising the amino acid sequence of MQALQTPLT (SEQ ID NO:3).In certain embodiments, the antigen-binding domain that specificallybinds to OX40 (e.g., human OX40) specifically binds to the same epitopeof OX40 (e.g., human OX40) as an antibody comprising a VH comprising theamino acid sequence of SEQ ID NO:16 and a VL comprising the amino acidsequence of SEQ ID NO:15. In certain embodiments, the antigen-bindingdomain that specifically binds to OX40 (e.g., human OX40) exhibits, ascompared to binding to a human OX40 sequence of SEQ ID NO:55, reduced orabsent binding to a protein identical to SEQ ID NO:55 except for thepresence of an amino acid mutation selected from the group consistingof: N60A, R62A, R80A, L88A, P93A, P99A, P115A, and a combinationthereof. In certain embodiments, the antigen-binding domain thatspecifically binds to OX40 (e.g., human OX40) comprises a VH and a VL,wherein the VH comprises the amino acid sequence of SEQ ID NO:16. Incertain embodiments, the antigen-binding domain that specifically bindsto OX40 (e.g., human OX40) comprises a VH and a VL, wherein the VLcomprises the amino acid sequence of SEQ ID NO:15. In certainembodiments, the antigen-binding domain that binds to OX40 comprises aVH comprising an amino acid sequence that is at least 75%, 80%, 85%,90%, 95%, or 99% identical to the amino acid sequence of SEQ ID NO:16.In certain embodiments, the antigen-binding domain that specificallybinds to OX40 (e.g., human OX40) comprises a VH comprising the aminoacid sequence of SEQ ID NO:16. In certain embodiments, theantigen-binding domain that binds to OX40 comprises a VH comprising anamino acid sequence derived from a human IGHV3-73 germline sequence(e.g., IGHV3-73*01, e.g., having the amino acid sequence of SEQ IDNO:19). In certain embodiments, the antigen-binding domain thatspecifically binds to OX40 (e.g., human OX40) comprises a VL comprisingan amino acid sequence that is at least 75%, 80%, 85%, 90%, 95%, or 99%identical to the amino acid sequence of SEQ ID NO:15. In certainembodiments, the antigen-binding domain that specifically binds to OX40(e.g., human OX40) comprises a VL-CDR3 comprising the amino acidsequence SEQ ID NO:3. In certain embodiments, the antigen-binding domainthat specifically binds to OX40 (e.g., human OX40) comprises a VLcomprising the amino acid sequence of SEQ ID NO:15. In certainembodiments, the antigen-binding domain that specifically binds to OX40(e.g., human OX40) comprises a light chain comprising the amino acidsequence of SEQ ID NO:20. In certain embodiments, the antigen-bindingdomain that specifically binds to OX40 (e.g., human OX40) comprises alight chain comprising the amino acid sequence of SEQ ID NO:50. Incertain embodiments, the antigen-binding domain that specifically bindsto OX40 (e.g., human OX40) comprises a VL comprising an amino acidsequence derived from a human IGKV2-28 germline sequence (e.g.,IGKV2-28*01, e.g., having the amino acid sequence of SEQ ID NO:18). Incertain embodiments, the antigen-binding domain that specifically bindsto OX40 (e.g., human OX40) comprises the VH and VL sequences set forthin SEQ ID NOs: 16 and 15, respectively. In certain embodiments, theantigen-binding domain that specifically binds to OX40 (e.g., humanOX40) comprises a heavy chain comprising the amino acid sequence of SEQID NO: 21. In certain embodiments, the antigen-binding domain thatspecifically binds to OX40 (e.g., human OX40) comprises a heavy chaincomprising the amino acid sequence of SEQ ID NO: 60. In certainembodiments, the antigen-binding domain that specifically binds to OX40(e.g., human OX40) comprises a mutation selected from the groupconsisting of a N297A, N297Q, D265A mutation, or a combination thereof.In certain embodiments, the antigen-binding domain that specificallybinds to OX40 (e.g., human OX40) comprises a mutation selected from thegroup consisting of D265A, P329A and a combination thereof.

In certain embodiments, an antagonistic antibody described herein isantagonistic to OX40 (e.g., human OX40). In certain embodiments, theantibody deactivates, reduces, or inhibits an activity of OX40 (e.g.,human OX40). In certain embodiments, the antibody inhibits or reducesbinding of OX40 (e.g., human OX40) to OX40 ligand (e.g., human OX40ligand). In certain embodiments, the antibody inhibits or reduces OX40(e.g., human OX40) signaling. In certain embodiments, the antibodyinhibits or reduces OX40 (e.g., human OX40) activity (e.g., OX40signaling) induced by OX40 ligand (e.g., human OX40 ligand). In certainembodiments, an antagonistic antibody described herein inhibits orreduces T cell proliferation. In certain embodiments, an antagonisticantibody described herein inhibits or reduces T cell proliferation. Incertain embodiments, an antagonistic antibody described herein inhibitsor reduces production of cytokines (e.g., inhibits or reduces productionof IL-2, TNFα, IFNγ, IL-4, IL-10, IL-13, or a combination thereof bystimulated T cells). In certain embodiments, an antagonistic antibodydescribed herein inhibits or reduces production of IL-2 bySEA-stimulated T cells. In certain embodiments, an antagonistic antibodydescribed herein blocks the interaction of OX40 and OX40L (e.g., blocksthe binding of OX40L and OX40 to one another, e.g., blocks the bindingof human OX40 ligand and human OX40)).

In certain embodiments, an antagonistic antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), decreases OX40(e.g., human OX40) activity by at least about 1.2 fold, 1.3 fold, 1.4fold, 1.5 fold, 2 fold, 2.5 fold, 3 fold, 3.5 fold, 4 fold, 4.5 fold, 5fold, 6 fold, 7 fold, 8 fold, 9 fold, 10 fold, 15 fold, 20 fold, 30fold, 40 fold, 50 fold, 60 fold, 70 fold, 80 fold, 90 fold, or 100 foldas assessed by methods described herein and/or known to one of skill inthe art, relative to OX40 (e.g., human OX40) activity without anyantibody or with an unrelated antibody (e.g., an antibody that does notimmunospecifically bind to OX40). In certain embodiments, anantagonistic antibody described herein, which immunospecifically bindsto OX40 (e.g., human OX40), decreases OX40 (e.g., human OX40) activityby at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%,65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99% as assessed by methodsdescribed herein and/or known to one of skill in the art, relative toOX40 (e.g., human OX40) activity without any antibody or with anunrelated antibody (e.g., an antibody that does not immunospecificallybind to OX40). Non-limiting examples of OX40 (e.g., human OX40) activitycan include OX40 (e.g., human OX40) signaling, cell proliferation, cellsurvival, and cytokine production (e.g., IL-2, TNF-α, IFN-γ, IL-4,IL-10, and/or IL-13). In certain embodiments, an antagonistic antibodydescribed herein, which immunospecifically binds to OX40 (e.g., humanOX40), inhibits, reduces, or inactivates an OX40 (e.g., human OX40)activity. In specific embodiments, OX40 activity is assessed asdescribed in the Examples, infra.

In certain aspects, an antagonistic antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), inhibits, reduces,or deactivates the cellular proliferation of cells that express OX40 andthat respond to OX40 signaling (e.g., cells that proliferate in responseto OX40 stimulation and OX40 signaling, such as T cells). Cellproliferation assays are described in the art, such as a ³H-thymidineincorporation assay, BrdU incorporation assay, or CFSE assay, such asdescribed in the Examples, infra, and can be readily carried out by oneof skill in the art. In specific embodiments, T cells (e.g., CD4⁺ orCD8⁺ effector T cells) stimulated with a T cell mitogen or T cellreceptor complex stimulating agent (e.g., phytohaemagglutinin (PHA)and/or phorbol myristate acetate (PMA), or a TCR complex stimulatingantibody, such as an anti-CD3 antibody and anti-CD28 antibody), in thepresence of an antagonistic antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), have decreasedcellular proliferation relative to T cells only stimulated with the Tcell mitogen or T cell receptor complex stimulating agent, such asphytohaemagglutinin (PHA) and/or phorbol myristate acetate (PMA), or aTCR complex stimulating antibody, such as an anti-CD3 antibody andanti-CD28 antibody.

In certain aspects, an antagonistic antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), decreases thesurvival of cells (e.g., T cells, such as CD4 and CD8 effector T cells).In a specific embodiment, T cells (e.g., CD4⁺ or CD8⁺ effector T cells)stimulated with a T cell mitogen or T cell receptor complex stimulatingagent (e.g., phytohaemagglutinin (PHA) and/or phorbol myristate acetate(PMA), or a TCR complex stimulating antibody, such as an anti-CD3antibody and anti-CD28 antibody) in the presence of an antagonisticantibody described herein, which immunospecifically binds to OX40 (e.g.,human OX40), have decreased survival relative to T cells only stimulatedwith the T cell mitogen. Cell survival assays are described in the art(e.g., a trypan blue exclusion assay) and can be readily carried out byone of skill in the art.

In specific embodiments, an antagonistic antibody described herein,which immunospecifically binds to OX40 (e.g., human OX40), decreasescell survival (e.g., T cells, such as CD4 and CD8 effector T cells) byat least about 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold, 2.5 fold,3 fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9fold, 10 fold, 15 fold, 20 fold, 30 fold, 40 fold, 50 fold, 60 fold, 70fold, 80 fold, 90 fold, or 100 fold, as assessed by methods describedherein or known to one of skill in the art (e.g., a trypan blueexclusion assay), without any antibody or with an unrelated antibody(e.g., an antibody that does not immunospecifically bind to OX40). Inspecific embodiments, an antagonistic antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), decreases cellsurvival (e.g., T cells, such as CD4 and CD8 effector T cells) by atleast about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%,65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99%, as assessed by methodsdescribed herein or known to one of skill in the art (e.g., a trypanblue exclusion assay), relative to OX40 (e.g., human OX40) activitywithout any antibody or with an unrelated antibody (e.g., an antibodythat does not immunospecifically bind to OX40).

In some embodiments, T cells (e.g., CD4⁺ or CD8⁺ effector T cells)stimulated with a T cell mitogen (e.g., an anti-CD3 antibody or phorbolester) in the presence of an antagonistic antibody described herein,which immunospecifically binds to OX40 (e.g., human OX40), havedecreased cell survival by at least about 1.2 fold, 1.3 fold, 1.4 fold,1.5 fold, 2 fold, 2.5 fold, 3 fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold,6 fold, 7 fold, 8 fold, 9 fold, 10 fold, 15 fold, 20 fold, 30 fold, 40fold, 50 fold, 60 fold, 70 fold, 80 fold, 90 fold, or 100 fold relativeto T cells only stimulated with the T cell mitogen or T cell receptorcomplex stimulating agent (e.g., phytohaemagglutinin (PHA) and/orphorbol myristate acetate (PMA), or a TCR complex stimulating antibody,such as an anti-CD3 antibody and anti-CD28 antibody), as assessed bymethods described herein or known to one of skill in the art (e.g., atrypan blue exclusion assay). In some embodiments, T cells (e.g., CD4⁺or CD8⁺ effector T cells) stimulated with a T cell mitogen or T cellreceptor complex stimulating agent (e.g., phytohaemagglutinin (PHA)and/or phorbol myristate acetate (PMA), or a TCR complex stimulatingantibody, such as an anti-CD3 antibody and anti-CD28 antibody) in thepresence of an antagonistic antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), have decreased cellsurvival by at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%,50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99% relativeto T cells only stimulated with the T cell mitogen, as assessed bymethods described herein or known to one of skill in the art (e.g., atrypan blue exclusion assay).

In certain embodiments, an antagonistic antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), does not protecteffector T cells (e.g., CD4⁺ and CD8⁺ effector T cells) fromactivation-induced cell death.

In specific embodiments, an antagonistic antibody described herein,which immunospecifically binds to OX40 (e.g., human OX40), inhibits,reduces, or deactivates cytokine production (e.g., IL-2, TNF-α, IFN-γ,IL-4, IL-10, and/or IL-13) by at least about 5%, 10%, 15%, 20%, 25%,30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%,98%, or 99%, as assessed by methods described herein (see the Examples,infra) or known to one of skill in the art, relative to cytokineproduction in the presence or absence of OX40L (e.g., human OX40L)stimulation without any antibody or with an unrelated antibody (e.g., anantibody that does not immunospecifically bind to OX40). In specificembodiments, an antagonistic antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), inhibits or reducescytokine production (e.g., IL-2, TNF-α, IFN-γ, IL-4, IL-10, and/orIL-13) by at least about 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold,2.5 fold, 3 fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8fold, 9 fold, 10 fold, 15 fold, 20 fold, 30 fold, 40 fold, 50 fold, 60fold, 70 fold, 80 fold, 90 fold, or 100 fold, as assessed by methodsdescribed herein (see the Examples, infra, such as Example 2) or knownto one of skill in the art, relative to cytokine production in thepresence or absence of OX40L (e.g., human OX40L) stimulation without anyantibody or with an unrelated antibody (e.g., an antibody that does notimmunospecifically bind to OX40).

In certain embodiments, T cells (e.g., CD4⁺ or CD8⁺ effector T cells)stimulated with a T cell mitogen or T cell receptor complex stimulatingagent (e.g., phytohaemagglutinin (PHA) and/or phorbol myristate acetate(PMA), or a TCR complex stimulating antibody, such as an anti-CD3antibody and anti-CD28 antibody) in the presence of an antagonisticantibody described herein, which immunospecifically binds to OX40 (e.g.,human OX40), have decreased cytokine production (e.g., IL-2, TNF-α,IFN-γ, IL-4, IL-10, and/or IL-13) by at least about 5%, 10%, 15%, 20%,25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%,95%, 98%, or 99% relative to T cells only stimulated with the T cellmitogen or T cell receptor complex stimulating agent (e.g.,phytohaemagglutinin (PHA) and/or phorbol myristate acetate (PMA), or aTCR complex stimulating antibody, such as an anti-CD3 antibody andanti-CD28 antibody), as assessed by methods described herein or known toone of skill in the art (e.g., an ELISA assay or as described in theExamples, infra). In some embodiments, T cells (e.g., CD4⁺ or CD8⁺effector T cells) stimulated with a T cell mitogen or T cell receptorcomplex stimulating agent (e.g., phytohaemagglutinin (PHA) and/orphorbol myristate acetate (PMA), or a TCR complex stimulating antibody,such as an anti-CD3 antibody and anti-CD28 antibody) in the presence ofan antagonistic antibody described herein, which immunospecificallybinds to OX40 (e.g., human OX40), have decreased cytokine production(e.g., IL-2, TNF-α, IFN-γ, IL-4, IL-10, and/or IL-13) by at least about1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold, 2.5 fold, 3 fold, 3.5fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, 10 fold,15 fold, 20 fold, 30 fold, 40 fold, 50 fold, 60 fold, 70 fold, 80 fold,90 fold, or 100 fold relative to T cells only stimulated with the T cellmitogen or T cell receptor complex stimulating agent (e.g.,phytohaemagglutinin (PHA) and/or phorbol myristate acetate (PMA), or aTCR complex stimulating antibody, such as an anti-CD3 antibody andanti-CD28 antibody), as assessed by methods described herein or known toone of skill in the art (e.g., an ELISA assay or as described in theExamples, infra).

In specific embodiments, an antagonistic antibody described herein,which immunospecifically binds to OX40 (e.g., human OX40), decreasesIL-2 production in response to Staphylococcus Enterotoxin A (SEA)stimulation by at least about 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2fold, 2.5 fold, 3 fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7fold, 8 fold, 9 fold, 10 fold, 15 fold, 20 fold, 30 fold, 40 fold, 50fold, 60 fold, 70 fold, 80 fold, 90 fold, or 100 fold, as assessed bymethods described herein (see the Examples, infra, such as Example 2) orknown to one of skill in the art, relative to IL-2 production withoutany antibody or with an unrelated antibody (e.g., an antibody that doesnot immunospecifically bind to OX40).

In certain embodiments, T cells (e.g., CD4⁺ or CD8⁺ T cells) stimulatedwith Staphylococcus Enterotoxin A (SEA) stimulation in the presence ofan antagonistic antibody described herein, which immunospecificallybinds to OX40 (e.g., human OX40), have decreased IL-2 production by atleast about 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 2 fold, 2.5 fold, 3fold, 3.5 fold, 4 fold, 4.5 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9fold, 10 fold, 15 fold, 20 fold, 30 fold, 40 fold, 50 fold, 60 fold, 70fold, 80 fold, 90 fold, or 100 fold relative to T cells only stimulatedwith SEA, as assessed by methods described herein or known to one ofskill in the art (e.g., an ELISA assay or as described in the Examples,infra).

An anti-OX40 antibody can be fused or conjugated (e.g., covalently ornoncovalently linked) to a detectable label or substance. Examples ofdetectable labels or substances include enzyme labels, such as, glucoseoxidase; radioisotopes, such as iodine (¹²⁵I, ¹³¹I), carbon (¹⁴C),sulfur (³⁵S), tritium (³H), indium (¹²¹In), and technetium (⁹⁹Tc);luminescent labels, such as luminol; and fluorescent labels, such asfluorescein and rhodamine, and biotin. Such labeled antibodies can beused to detect OX40 (e.g., human OX40) protein. See, e.g., Section5.5.2, infra.

5.3 Antibody Production

Antibodies that immunospecifically bind to OX40 (e.g., human OX40) canbe produced by any method known in the art for the synthesis ofantibodies, for example, by chemical synthesis or by recombinantexpression techniques. The methods described herein employ, unlessotherwise indicated, conventional techniques in molecular biology,microbiology, genetic analysis, recombinant DNA, organic chemistry,biochemistry, PCR, oligonucleotide synthesis and modification, nucleicacid hybridization, and related fields within the skill of the art.These techniques are described, for example, in the references citedherein and are fully explained in the literature. See, e.g., Maniatis Tet al., (1982) Molecular Cloning: A Laboratory Manual, Cold SpringHarbor Laboratory Press; Sambrook J et al., (1989), Molecular Cloning: ALaboratory Manual, Second Edition, Cold Spring Harbor Laboratory Press;Sambrook J et al., (2001) Molecular Cloning: A Laboratory Manual, ColdSpring Harbor Laboratory Press, Cold Spring Harbor, N.Y.; Ausubel F M etal., Current Protocols in Molecular Biology, John Wiley & Sons (1987 andannual updates); Current Protocols in Immunology, John Wiley & Sons(1987 and annual updates) Gait (ed.) (1984) Oligonucleotide Synthesis: APractical Approach, IRL Press; Eckstein (ed.) (1991) Oligonucleotidesand Analogues: A Practical Approach, IRL Press; Birren B et al., (eds.)(1999) Genome Analysis: A Laboratory Manual, Cold Spring HarborLaboratory Press.

In a specific embodiment, an antibody described herein is an antibody(e.g., recombinant antibody) prepared, expressed, created or isolated byany means that involves creation, e.g., via synthesis, geneticengineering of DNA sequences. In certain embodiments, such antibodycomprises sequences (e.g., DNA sequences or amino acid sequences) thatdo not naturally exist within the antibody germline repertoire of ananimal or mammal (e.g., human) in vivo.

In a certain aspect, provided herein is a method of making an antibodywhich immunospecifically binds to OX40 (e.g., human OX40) comprisingculturing a cell or host cell described herein. In a certain aspect,provided herein is a method of making an antibody whichimmunospecifically binds to OX40 (e.g., human OX40) comprisingexpressing (e.g., recombinantly expressing) the antibody using a cell orhost cell described herein (e.g., a cell or a host cell comprisingpolynucleotides encoding an antibody described herein). In a particularembodiment, the cell is an isolated cell. In a particular embodiment,the exogenous polynucleotides have been introduced into the cell. In aparticular embodiment, the method further comprises the step ofpurifying the antibody obtained from the cell or host cell.

Methods for producing polyclonal antibodies are known in the art (see,for example, Chapter 11 in: Short Protocols in Molecular Biology, (2002)5th Ed., Ausubel F M et al., eds., John Wiley and Sons, New York).

Monoclonal antibodies can be prepared using a wide variety of techniquesknown in the art including the use of hybridoma, recombinant, and phagedisplay technologies, or a combination thereof. For example, monoclonalantibodies can be produced using hybridoma techniques including thoseknown in the art and taught, for example, in Harlow E & Lane D,Antibodies: A Laboratory Manual, (Cold Spring Harbor Laboratory Press,2nd ed. 1988); Hammerling G J et al., in: Monoclonal Antibodies andT-Cell Hybridomas 563 681 (Elsevier, N.Y., 1981). The term “monoclonalantibody” as used herein is not limited to antibodies produced throughhybridoma technology. For example, monoclonal antibodies can be producedrecombinantly from host cells exogenously expressing an antibodydescribed herein.

In specific embodiments, a “monoclonal antibody,” as used herein, is anantibody produced by a single cell (e.g., hybridoma or host cellproducing a recombinant antibody), wherein the antibodyimmunospecifically binds to OX40 (e.g., human OX40) as determined, e.g.,by ELISA or other antigen-binding or competitive binding assay known inthe art or in the Examples provided herein. In particular embodiments, amonoclonal antibody can be a chimeric antibody or a humanized antibody.In certain embodiments, a monoclonal antibody is a monovalent antibodyor multivalent (e.g., bivalent) antibody. In certain embodiments, amonoclonal antibody can be a Fab fragment or a F(ab′)₂ fragment.Monoclonal antibodies described herein can, for example, be made by thehybridoma method as described in Kohler G & Milstein C (1975) Nature256: 495 or can, e.g., be isolated from phage libraries using thetechniques as described herein, for example. Other methods for thepreparation of clonal cell lines and of monoclonal antibodies expressedthereby are well known in the art (see, for example, Chapter 11 in:Short Protocols in Molecular Biology, (2002) 5th Ed., Ausubel F M etal., supra).

Methods for producing and screening for specific antibodies usinghybridoma technology are routine and well known in the art. For example,in the hybridoma method, a mouse or other appropriate host animal, suchas a sheep, goat, rabbit, rat, hamster or macaque monkey, is immunizedto elicit lymphocytes that produce or are capable of producingantibodies that will specifically bind to the protein (e.g., OX40 (e.g.,human OX40)) used for immunization. Alternatively, lymphocytes may beimmunized in vitro. Lymphocytes then are fused with myeloma cells usinga suitable fusing agent, such as polyethylene glycol, to form ahybridoma cell (Goding J W (Ed), Monoclonal Antibodies: Principles andPractice, pp. 59-103 (Academic Press, 1986)). Additionally, a RIMMS(repetitive immunization multiple sites) technique can be used toimmunize an animal (Kilpatrick K E et al., (1997) Hybridoma 16:381-9,incorporated by reference in its entirety).

In some embodiments, mice (or other animals, such as rats, monkeys,donkeys, pigs, sheep, hamster, or dogs) can be immunized with an antigen(e.g., OX40 (e.g., human OX40)) and once an immune response is detected,e.g., antibodies specific for the antigen are detected in the mouseserum, the mouse spleen is harvested and splenocytes isolated. Thesplenocytes are then fused by well known techniques to any suitablemyeloma cells, for example cells from cell line SP20 available from theAmerican Type Culture Collection (ATCC®) (Manassas, Va.), to formhybridomas. Hybridomas are selected and cloned by limited dilution. Incertain embodiments, lymph nodes of the immunized mice are harvested andfused with NS0 myeloma cells.

The hybridoma cells thus prepared are seeded and grown in a suitableculture medium that preferably contains one or more substances thatinhibit the growth or survival of the unfused, parental myeloma cells.For example, if the parental myeloma cells lack the enzyme hypoxanthineguanine phosphoribosyl transferase (HGPRT or HPRT), the culture mediumfor the hybridomas typically will include hypoxanthine, aminopterin, andthymidine (HAT medium), which substances prevent the growth ofHGPRT-deficient cells.

Specific embodiments employ myeloma cells that fuse efficiently, supportstable high-level production of antibody by the selectedantibody-producing cells, and are sensitive to a medium such as HATmedium. Among these myeloma cell lines are murine myeloma lines, such asNS0 cell line or those derived from MOPC-21 and MPC-11 mouse tumorsavailable from the Salk Institute Cell Distribution Center, San Diego,Calif., USA, and SP-2 or X63-Ag8.653 cells available from the AmericanType Culture Collection, Rockville, Md., USA. Human myeloma andmouse-human heteromyeloma cell lines also have been described for theproduction of human monoclonal antibodies (Kozbor D (1984) J Immunol133: 3001-5; Brodeur et al., Monoclonal Antibody Production Techniquesand Applications, pp. 51-63 (Marcel Dekker, Inc., New York, 1987)).

Culture medium in which hybridoma cells are growing is assayed forproduction of monoclonal antibodies directed against OX40 (e.g., humanOX40). The binding specificity of monoclonal antibodies produced byhybridoma cells is determined by methods known in the art, for example,immunoprecipitation or by an in vitro binding assay, such asradioimmunoassay (MA) or enzyme-linked immunoabsorbent assay (ELISA).

After hybridoma cells are identified that produce antibodies of thedesired specificity, affinity, and/or activity, the clones may besubcloned by limiting dilution procedures and grown by standard methods(Goding J W (Ed), Monoclonal Antibodies: Principles and Practice,supra). Suitable culture media for this purpose include, for example,D-MEM or RPMI 1640 medium. In addition, the hybridoma cells may be grownin vivo as ascites tumors in an animal.

The monoclonal antibodies secreted by the subclones are suitablyseparated from the culture medium, ascites fluid, or serum byconventional immunoglobulin purification procedures such as, forexample, protein A-Sepharose, hydroxylapatite chromatography, gelelectrophoresis, dialysis, or affinity chromatography.

Antibodies described herein can be generated by any technique known tothose of skill in the art. For example, Fab and F(ab′)₂ fragmentsdescribed herein can be produced by proteolytic cleavage ofimmunoglobulin molecules, using enzymes such as papain (to produce Fabfragments) or pepsin (to produce F(ab′)₂ fragments). A Fab fragmentcorresponds to one of the two identical arms of a tetrameric antibodymolecule and contains the complete light chain paired with the VH andCH1 domains of the heavy chain. A F(ab′)₂ fragment contains the twoantigen-binding arms of a tetrameric antibody molecule linked bydisulfide bonds in the hinge region.

Further, the antibodies described herein can also be generated usingvarious phage display methods known in the art. In phage displaymethods, proteins are displayed on the surface of phage particles whichcarry the polynucleotide sequences encoding them. In particular, DNAsequences encoding VH and VL domains are amplified from animal cDNAlibraries (e.g., human or murine cDNA libraries of affected tissues).The DNA encoding the VH and VL domains are recombined together with ascFv linker by PCR and cloned into a phagemid vector. The vector iselectroporated in E. coli and the E. coli is infected with helper phage.Phage used in these methods are typically filamentous phage including fdand M13, and the VH and VL domains are usually recombinantly fused toeither the phage gene III or gene VIII. Phage expressing an antibodythat binds to a particular antigen can be selected or identified withantigen, e.g., using labeled antigen or antigen bound or captured to asolid surface or bead. Examples of phage display methods that can beused to make the antibodies described herein include those disclosed inBrinkman U et al., (1995) J Immunol Methods 182: 41-50; Ames R S et al.,(1995) J Immunol Methods 184: 177-186; Kettleborough C A et al., (1994)Eur J Immunol 24: 952-958; Persic L et al., (1997) Gene 187: 9-18;Burton D R & Barbas C F (1994) Advan Immunol 57: 191-280; PCTApplication No. PCT/GB91/001134; International Publication Nos. WO90/02809, WO 91/10737, WO 92/01047, WO 92/18619, WO 93/1 1236, WO95/15982, WO 95/20401, and WO 97/13844; and U.S. Pat. Nos. 5,698,426,5,223,409, 5,403,484, 5,580,717, 5,427,908, 5,750,753, 5,821,047,5,571,698, 5,427,908, 5,516,637, 5,780,225, 5,658,727, 5,733,743, and5,969,108.

As described in the above references, after phage selection, theantibody coding regions from the phage can be isolated and used togenerate antibodies, including human antibodies, and expressed in anydesired host, including mammalian cells, insect cells, plant cells,yeast, and bacteria, e.g., as described below. Techniques torecombinantly produce antibodies such as Fab, Fab′ and F(ab′)₂ fragmentscan also be employed using methods known in the art such as thosedisclosed in PCT publication No. WO 92/22324; Mullinax R L et al.,(1992) BioTechniques 12(6): 864-9; Sawai H et al., (1995) Am J ReprodImmunol 34: 26-34; and Better M et al., (1988) Science 240: 1041-1043.

In one aspect, to generate antibodies, PCR primers including VH or VLnucleotide sequences, a restriction site, and a flanking sequence toprotect the restriction site can be used to amplify the VH or VLsequences from a template, e.g., scFv clones. Utilizing cloningtechniques known to those of skill in the art, the PCR amplified VHdomains can be cloned into vectors expressing a VH constant region, andthe PCR amplified VL domains can be cloned into vectors expressing a VLconstant region, e.g., human kappa or lambda constant regions. The VHand VL domains can also be cloned into one vector expressing thenecessary constant regions. The heavy chain conversion vectors and lightchain conversion vectors are then co-transfected into cell lines togenerate stable or transient cell lines that express antibodies, e.g.,IgG, using techniques known to those of skill in the art.

A chimeric antibody is a molecule in which different portions of theantibody are derived from different immunoglobulin molecules. Forexample, a chimeric antibody can contain a variable region of a mouse orrat monoclonal antibody fused to a constant region of a human antibody.Methods for producing chimeric antibodies are known in the art. See,e.g., Morrison S L (1985) Science 229: 1202-7; Oi V T & Morrison S L(1986) BioTechniques 4: 214-221; Gillies S D et al., (1989) J ImmunolMethods 125: 191-202; and U.S. Pat. Nos. 5,807,715, 4,816,567,4,816,397, and 6,331,415.

A humanized antibody is capable of binding to a predetermined antigenand which comprises a framework region having substantially the aminoacid sequence of a human immunoglobulin and CDRs having substantiallythe amino acid sequence of a non-human immunoglobulin (e.g., a murineimmunoglobulin). In particular embodiments, a humanized antibody alsocomprises at least a portion of an immunoglobulin constant region (Fc),typically that of a human immunoglobulin. The antibody also can includethe CH1, hinge, CH2, CH3, and CH4 regions of the heavy chain. Ahumanized antibody can be selected from any class of immunoglobulins,including IgM, IgG, IgD, IgA and IgE, and any isotype, including IgG₁,IgG₂, IgG₃ and IgG₄. Humanized antibodies can be produced using avariety of techniques known in the art, including but not limited to,CDR-grafting (European Patent No. EP 239400; International PublicationNo. WO 91/09967; and U.S. Pat. Nos. 5,225,539, 5,530,101, and5,585,089), veneering or resurfacing (European Patent Nos. EP 592106 andEP 519596; Padlan E A (1991) Mol Immunol 28(4/5): 489-498; Studnicka G Met al., (1994) Prot Engineering 7(6): 805-814; and Roguska M A et al.,(1994) PNAS 91: 969-973), chain shuffling (U.S. Pat. No. 5,565,332), andtechniques disclosed in, e.g., U.S. Pat. Nos. 6,407,213, 5,766,886,International Publication No. WO 93/17105; Tan P et al., (2002) JImmunol 169: 1119-25; Caldas C et al., (2000) Protein Eng. 13(5):353-60; Morea V et al., (2000) Methods 20(3): 267-79; Baca M et al.,(1997) J Biol Chem 272(16): 10678-84; Roguska M A et al., (1996) ProteinEng 9(10): 895 904; Couto J R et al., (1995) Cancer Res. 55 (23 Supp):5973s-5977s; Couto J R et al., (1995) Cancer Res 55(8): 1717-22; SandhuJ S (1994) Gene 150(2): 409-10 and Pedersen J T et al., (1994) J MolBiol 235(3): 959-73. See also U.S. Application Publication No. US2005/0042664 A1 (Feb. 24, 2005), which is incorporated by referenceherein in its entirety.

Single domain antibodies, for example, antibodies lacking the lightchains, can be produced by methods well known in the art. See RiechmannL & Muyldermans S (1999) J Immunol 231: 25-38; Nuttall S D et al.,(2000) Curr Pharm Biotechnol 1(3): 253-263; Muyldermans S, (2001) JBiotechnol 74(4): 277-302; U.S. Pat. No. 6,005,079; and InternationalPublication Nos. WO 94/04678, WO 94/25591 and WO 01/44301.

Further, antibodies that immunospecifically bind to a OX40 antigen can,in turn, be utilized to generate anti-idiotype antibodies that “mimic”an antigen using techniques well known to those skilled in the art.(See, e.g., Greenspan N S & Bona C A (1989) FASEB J 7(5): 437-444; andNissinoff A (1991) J Immunol 147(8): 2429-2438).

In particular embodiments, an antibody described herein, which binds tothe same epitope of OX40 (e.g., human OX40) as an anti-OX40 antibodydescribed herein, is a human antibody. In particular embodiments, anantibody described herein, which competitively blocks (e.g., in adose-dependent manner) any one of the antibodies described herein,(e.g., pab1949 or pab2044) from binding to OX40 (e.g., human OX40), is ahuman antibody. Human antibodies can be produced using any method knownin the art. For example, transgenic mice which are incapable ofexpressing functional endogenous immunoglobulins, but which can expresshuman immunoglobulin genes, can be used. In particular, the human heavyand light chain immunoglobulin gene complexes can be introduced randomlyor by homologous recombination into mouse embryonic stem cells.Alternatively, the human variable region, constant region, and diversityregion can be introduced into mouse embryonic stem cells in addition tothe human heavy and light chain genes. The mouse heavy and light chainimmunoglobulin genes can be rendered non-functional separately orsimultaneously with the introduction of human immunoglobulin loci byhomologous recombination. In particular, homozygous deletion of theJ_(H) region prevents endogenous antibody production. The modifiedembryonic stem cells are expanded and microinjected into blastocysts toproduce chimeric mice. The chimeric mice are then bred to producehomozygous offspring which express human antibodies. The transgenic miceare immunized in the normal fashion with a selected antigen, e.g., allor a portion of an antigen (e.g., OX40). Monoclonal antibodies directedagainst the antigen can be obtained from the immunized, transgenic miceusing conventional hybridoma technology. The human immunoglobulintransgenes harbored by the transgenic mice rearrange during B celldifferentiation, and subsequently undergo class switching and somaticmutation. Thus, using such a technique, it is possible to producetherapeutically useful IgG, IgA, IgM and IgE antibodies. For an overviewof this technology for producing human antibodies, see Lonberg N &Huszar D (1995) Int Rev Immunol 13:65-93. For a detailed discussion ofthis technology for producing human antibodies and human monoclonalantibodies and protocols for producing such antibodies, see, e.g.,International Publication Nos. WO 98/24893, WO 96/34096 and WO 96/33735;and U.S. Pat. Nos. 5,413,923, 5,625,126, 5,633,425, 5,569,825,5,661,016, 5,545,806, 5,814,318 and 5,939,598. Examples of mice capableof producing human antibodies include the Xenomouse™ (Abgenix, Inc.;U.S. Pat. Nos. 6,075,181 and 6,150,184), the HuAb-Mouse™ (Mederex,Inc./Gen Pharm; U.S. Pat. Nos. 5,545,806 and 5,569,825), the TransChromo Mouse™ (Kirin) and the KM Mouse™ (Medarex/Kirin).

Human antibodies which specifically bind to OX40 (e.g., human OX40) canbe made by a variety of methods known in the art including phage displaymethods described above using antibody libraries derived from humanimmunoglobulin sequences. See also U.S. Pat. Nos. 4,444,887, 4,716,111,and 5,885,793; and International Publication Nos. WO 98/46645, WO98/50433, WO 98/24893, WO 98/16654, WO 96/34096, WO 96/33735, and WO91/10741.

In some embodiments, human antibodies can be produced using mouse-humanhybridomas. For example, human peripheral blood lymphocytes transformedwith Epstein-Barr virus (EBV) can be fused with mouse myeloma cells toproduce mouse-human hybridomas secreting human monoclonal antibodies,and these mouse-human hybridomas can be screened to determine ones whichsecrete human monoclonal antibodies that immunospecifically bind to atarget antigen (e.g., OX40 (e.g., human OX40)). Such methods are knownand are described in the art, see, e.g., Shinmoto H et al., (2004)Cytotechnology 46: 19-23; Naganawa Y et al., (2005) Human Antibodies 14:27-31.

5.3.1 Polynucleotides

In certain aspects, provided herein are polynucleotides comprising anucleotide sequence encoding an antibody described herein or a fragmentthereof (e.g., a variable light chain region and/or variable heavy chainregion) that immunospecifically binds to an OX40 (e.g., human OX40)antigen, and vectors, e.g., vectors comprising such polynucleotides forrecombinant expression in host cells (e.g., E. coli and mammaliancells). Provided herein are polynucleotides comprising nucleotidesequences encoding any of the antibodies provided herein, as well asvectors comprising such polynucleotide sequences, e.g., expressionvectors for their efficient expression in host cells, e.g., mammaliancells.

As used herein, an “isolated” polynucleotide or nucleic acid molecule isone which is separated from other nucleic acid molecules which arepresent in the natural source (e.g., in a mouse or a human) of thenucleic acid molecule. Moreover, an “isolated” nucleic acid molecule,such as a cDNA molecule, can be substantially free of other cellularmaterial, or culture medium when produced by recombinant techniques, orsubstantially free of chemical precursors or other chemicals whenchemically synthesized. For example, the language “substantially free”includes preparations of polynucleotide or nucleic acid molecule havingless than about 15%, 10%, 5%, 2%, 1%, 0.5%, or 0.1% (in particular lessthan about 10%) of other material, e.g., cellular material, culturemedium, other nucleic acid molecules, chemical precursors and/or otherchemicals. In a specific embodiment, a nucleic acid molecule(s) encodingan antibody described herein is isolated or purified.

In particular aspects, provided herein are polynucleotides comprisingnucleotide sequences encoding antibodies, which immunospecifically bindto an OX40 polypeptide (e.g., human OX40) and comprises an amino acidsequence as described herein, as well as antibodies that compete withsuch antibodies for binding to an OX40 polypeptide (e.g., in adose-dependent manner), or which binds to the same epitope as that ofsuch antibodies.

In certain aspects, provided herein are polynucleotides comprising anucleotide sequence encoding the light chain or heavy chain of anantibody described herein. The polynucleotides can comprise nucleotidesequences encoding a light chain comprising the VL FRs and CDRs ofantibodies described herein (see, e.g., Tables 1 and 3). Thepolynucleotides can comprise nucleotide sequences encoding a heavy chaincomprising the VH FRs and CDRs of antibodies described herein (see,e.g., Tables 2 and 4). In specific embodiments, a polynucleotidedescribed herein encodes a VL domain comprising the amino acid sequenceset forth in SEQ ID NO: 15. In specific embodiments, a polynucleotidedescribed herein encodes a VH domain comprising the amino acid sequenceset forth in SEQ ID NO: 16.

In particular embodiments, provided herein are polynucleotidescomprising a nucleotide sequence encoding an anti-OX40 antibodycomprising three VL chain CDRs, e.g., containing VL CDR1, VL CDR2, andVL CDR3 of any one of antibodies described herein (e.g., see Table 1).In specific embodiments, provided herein are polynucleotides comprisingthree VH chain CDRs, e.g., containing VH CDR1, VH CDR2, and VH CDR3 ofany one of antibodies described herein (e.g., see Table 2). In specificembodiments, provided herein are polynucleotides comprising a nucleotidesequence encoding an anti-OX40 antibody comprising three VH chain CDRs,e.g., containing VL CDR1, VL CDR2, and VL CDR3 of any one of antibodiesdescribed herein (e.g., see Table 1) and three VH chain CDRs, e.g.,containing VH CDR1, VH CDR2, and VH CDR3 of any one of antibodiesdescribed herein (e.g., see Table 2).

In particular embodiments, provided herein are polynucleotidescomprising a nucleotide sequence encoding an anti-OX40 antibody or afragment thereof comprising a VL domain, e.g., containingFR1-CDR1-FR2-CDR2-FR3-CDR3-FR4, comprising an amino acid sequencedescribed herein (e.g., see Tables 1 and 3, e.g., the VL CDRs and VLFRsof a particular antibody identified by name in the tables). In specificembodiments, provided herein are polynucleotides comprising a nucleotidesequence encoding an anti-OX40 antibody or a fragment thereof comprisinga VH domain, e.g., containing FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4, comprisingan amino acid sequence described herein (e.g., see Tables 2 and 4, e.g.,the VH CDRs and VH FRs of a particular antibody identified by name inthe Tables).

In certain embodiments, a polynucleotide described herein comprises anucleotide sequence encoding an antibody provided herein comprising alight chain variable region comprising an amino acid sequence describedherein (e.g., SEQ ID NO: 15), wherein the antibody immunospecificallybinds to OX40 (e.g., human OX40). In a certain embodiment, apolynucleotide described herein comprises a nucleotide sequence encodingantibody pab1949 or pab2044 provided herein or a fragment thereofcomprising a light chain variable region comprising an amino acidsequence described herein (e.g., SEQ ID NO: 15).

In certain embodiments, a polynucleotide described herein comprises anucleotide sequence encoding an antibody provided herein comprising aheavy chain variable region comprising an amino acid sequence describedherein (e.g., SEQ ID NO: 16), wherein the antibody immunospecificallybinds to OX40 (e.g., human OX40). In a certain embodiment, apolynucleotide described herein comprises a nucleotide sequence encodingantibody pab1949 or pab2044 provided herein or a fragment thereofcomprising a heavy chain variable region comprising an amino acidsequence described herein (e.g., SEQ ID NO: 16).

In certain aspects, a polynucleotide comprises a nucleotide sequenceencoding an antibody or fragment thereof described herein comprising aVL domain comprising one or more VL FRs having the amino acid sequencedescribed herein (e.g., see Table 3), wherein the antibodyimmunospecifically binds to OX40 (e.g., human OX40). In certain aspects,a polynucleotide comprises a nucleotide sequence encoding an antibody orfragment thereof described herein comprising a VH domain comprising oneor more VH FRs having the amino acid sequence described herein (e.g.,see Table 4), wherein the antibody immunospecifically binds to OX40(e.g., human OX40).

In specific embodiments, a polynucleotide provided herein comprises anucleotide sequence encoding an antibody or fragment thereof describedherein comprising: framework regions (e.g., framework regions of the VLdomain and VH domain) that are human framework regions, wherein theantibody immunospecifically binds OX40 (e.g., human OX40). In certainembodiments, a polynucleotide provided herein comprises a nucleotidesequence encoding an antibody or fragment thereof (e.g., CDRs orvariable domain) described in Section 5.2 above.

In specific aspects, provided herein is a polynucleotide comprising anucleotide sequence encoding an antibody comprising a light chain and aheavy chain, e.g., a separate light chain and heavy chain. With respectto the light chain, in a specific embodiment, a polynucleotide providedherein comprises a nucleotide sequence encoding a kappa light chain. Inanother specific embodiment, a polynucleotide provided herein comprisesa nucleotide sequence encoding a lambda light chain. In yet anotherspecific embodiment, a polynucleotide provided herein comprises anucleotide sequence encoding an antibody described herein comprising ahuman kappa light chain or a human lambda light chain. In a particularembodiment, a polynucleotide provided herein comprises a nucleotidesequence encoding an antibody, which immunospecifically binds to OX40(e.g., human OX40), wherein the antibody comprises a light chain, andwherein the amino acid sequence of the VL domain can comprise the aminoacid sequence set forth in SEQ ID NO: 15 and wherein the constant regionof the light chain comprises the amino acid sequence of a human kappalight chain constant region. In another particular embodiment, apolynucleotide provided herein comprises a nucleotide sequence encodingan antibody, which immunospecifically binds to OX40 (e.g., human OX40),and comprises a light chain, wherein the amino acid sequence of the VLdomain can comprise the amino acid sequence set forth in SEQ ID NO: 15,and wherein the constant region of the light chain comprises the aminoacid sequence of a human lambda light chain constant region. Forexample, human constant region sequences can be those described in U.S.Pat. No. 5,693,780.

In a particular embodiment, a polynucleotide provided herein comprises anucleotide sequence encoding an antibody described herein, whichimmunospecifically binds to OX40 (e.g., human OX40), wherein theantibody comprises a heavy chain, wherein the amino acid sequence of theVH domain can comprise the amino acid sequence set forth in SEQ ID NO:16, and wherein the constant region of the heavy chain comprises theamino acid sequence of a human gamma (γ) heavy chain constant region.

In a certain embodiment, a polynucleotide provided herein comprises anucleotide sequence(s) encoding a VH domain and/or a VL domain of anantibody described herein (e.g., pa91949 or pab2044 such as SEQ ID NO:16 for the VH domain or SEQ ID NO: 15 for the VL domain), whichimmunospecifically binds to OX40 (e.g., human OX40).

In yet another specific embodiment, a polynucleotide provided hereincomprises a nucleotide sequence encoding an antibody described herein,which immunospecifically binds OX40 (e.g., human OX40), wherein theantibody comprises a VL domain and a VH domain comprising any amino acidsequences described herein, and wherein the constant regions comprisethe amino acid sequences of the constant regions of a human IgG₁ (e.g.,allotype 1, 17, or 3), human IgG₂, or human IgG₄.

In a specific embodiment, provided herein are polynucleotides comprisinga nucleotide sequence encoding an anti-OX40 antibody or domain thereof,designated herein, see, e.g., Tables 1-4, for example antibody pab1949or pab2044.

Also provided herein are polynucleotides encoding an anti-OX40 antibodyor a fragment thereof that are optimized, e.g., by codon/RNAoptimization, replacement with heterologous signal sequences, andelimination of mRNA instability elements. Methods to generate optimizednucleic acids encoding an anti-OX40 antibody or a fragment thereof(e.g., light chain, heavy chain, VH domain, or VL domain) forrecombinant expression by introducing codon changes and/or eliminatinginhibitory regions in the mRNA can be carried out by adapting theoptimization methods described in, e.g., U.S. Pat. Nos. 5,965,726;6,174,666; 6,291,664; 6,414,132; and 6,794,498, accordingly. Forexample, potential splice sites and instability elements (e.g., A/T orA/U rich elements) within the RNA can be mutated without altering theamino acids encoded by the nucleic acid sequences to increase stabilityof the RNA for recombinant expression. The alterations utilize thedegeneracy of the genetic code, e.g., using an alternative codon for anidentical amino acid. In some embodiments, it can be desirable to alterone or more codons to encode a conservative mutation, e.g., a similaramino acid with similar chemical structure and properties and/orfunction as the original amino acid.

In certain embodiments, an optimized polynucleotide sequence encoding ananti-OX40 antibody described herein or a fragment thereof (e.g., VLdomain or VH domain) can hybridize to an antisense (e.g., complementary)polynucleotide of an unoptimized polynucleotide sequence encoding ananti-OX40 antibody described herein or a fragment thereof (e.g., VLdomain or VH domain). In specific embodiments, an optimized nucleotidesequence encoding an anti-OX40 antibody described herein or a fragmenthybridizes under high stringency conditions to antisense polynucleotideof an unoptimized polynucleotide sequence encoding an anti-OX40 antibodydescribed herein or a fragment thereof. In a specific embodiment, anoptimized nucleotide sequence encoding an anti-OX40 antibody describedherein or a fragment thereof hybridizes under high stringency,intermediate or lower stringency hybridization conditions to anantisense polynucleotide of an unoptimized nucleotide sequence encodingan anti-OX40 antibody described herein or a fragment thereof.Information regarding hybridization conditions has been described, see,e.g., U.S. Patent Application Publication No. US 2005/0048549 (e.g.,paragraphs 72-73), which is incorporated herein by reference.

The polynucleotides can be obtained, and the nucleotide sequence of thepolynucleotides determined, by any method known in the art. Nucleotidesequences encoding antibodies described herein, e.g., antibodiesdescribed in Tables 1-4, and modified versions of these antibodies canbe determined using methods well known in the art, i.e., nucleotidecodons known to encode particular amino acids are assembled in such away to generate a nucleic acid that encodes the antibody. Such apolynucleotide encoding the antibody can be assembled from chemicallysynthesized oligonucleotides (e.g., as described in Kutmeier G et al.,(1994), BioTechniques 17: 242-246), which, briefly, involves thesynthesis of overlapping oligonucleotides containing portions of thesequence encoding the antibody, annealing and ligating of thoseoligonucleotides, and then amplification of the ligated oligonucleotidesby PCR.

Alternatively, a polynucleotide encoding an antibody or fragment thereofdescribed herein can be generated from nucleic acid from a suitablesource (e.g., a hybridoma) using methods well known in the art (e.g.,PCR and other molecular cloning methods). For example, PCR amplificationusing synthetic primers hybridizable to the 3′ and 5′ ends of a knownsequence can be performed using genomic DNA obtained from hybridomacells producing the antibody of interest. Such PCR amplification methodscan be used to obtain nucleic acids comprising the sequence encoding thelight chain and/or heavy chain of an antibody. Such PCR amplificationmethods can be used to obtain nucleic acids comprising the sequenceencoding the variable light chain region and/or the variable heavy chainregion of an antibody. The amplified nucleic acids can be cloned intovectors for expression in host cells and for further cloning, forexample, to generate chimeric and humanized antibodies.

If a clone containing a nucleic acid encoding a particular antibody orfragment thereof is not available, but the sequence of the antibodymolecule or fragment thereof is known, a nucleic acid encoding theimmunoglobulin or fragment can be chemically synthesized or obtainedfrom a suitable source (e.g., an antibody cDNA library or a cDNA librarygenerated from, or nucleic acid, preferably poly A+ RNA, isolated from,any tissue or cells expressing the antibody, such as hybridoma cellsselected to express an antibody described herein) by PCR amplificationusing synthetic primers hybridizable to the 3′ and 5′ ends of thesequence or by cloning using an oligonucleotide probe specific for theparticular gene sequence to identify, e.g., a cDNA clone from a cDNAlibrary that encodes the antibody. Amplified nucleic acids generated byPCR can then be cloned into replicable cloning vectors using any methodwell known in the art.

DNA encoding anti-OX40 antibodies described herein can be readilyisolated and sequenced using conventional procedures (e.g., by usingoligonucleotide probes that are capable of binding specifically to genesencoding the heavy and light chains of the anti-OX40 antibodies).Hybridoma cells can serve as a source of such DNA. Once isolated, theDNA can be placed into expression vectors, which are then transfectedinto host cells such as E. coli cells, simian COS cells, Chinese hamsterovary (CHO) cells (e.g., CHO cells from the CHO GS System™ (Lonza)), ormyeloma cells that do not otherwise produce immunoglobulin protein, toobtain the synthesis of anti-OX40 antibodies in the recombinant hostcells.

To generate antibodies, PCR primers including VH or VL nucleotidesequences, a restriction site, and a flanking sequence to protect therestriction site can be used to amplify the VH or VL sequences in scFvclones. Utilizing cloning techniques known to those of skill in the art,the PCR amplified VH domains can be cloned into vectors expressing aheavy chain constant region, e.g., the human gamma 4 constant region,and the PCR amplified VL domains can be cloned into vectors expressing alight chain constant region, e.g., human kappa or lambda constantregions. In certain embodiments, the vectors for expressing the VH or VLdomains comprise an EF-1α promoter, a secretion signal, a cloning sitefor the variable domain, constant domains, and a selection marker suchas neomycin. The VH and VL domains can also be cloned into one vectorexpressing the necessary constant regions. The heavy chain conversionvectors and light chain conversion vectors are then co-transfected intocell lines to generate stable or transient cell lines that expressfull-length antibodies, e.g., IgG, using techniques known to those ofskill in the art.

The DNA also can be modified, for example, by substituting the codingsequence for human heavy and light chain constant domains in place ofthe murine sequences, or by covalently joining to the immunoglobulincoding sequence all or part of the coding sequence for anon-immunoglobulin polypeptide.

Also provided are polynucleotides that hybridize under high stringency,intermediate or lower stringency hybridization conditions topolynucleotides that encode an antibody described herein. In specificembodiments, polynucleotides described herein hybridize under highstringency, intermediate or lower stringency hybridization conditions topolynucleotides encoding a VH domain (e.g., SEQ ID NO: 16) and/or VLdomain (e.g., SEQ ID NO: 15) provided herein.

Hybridization conditions have been described in the art and are known toone of skill in the art. For example, hybridization under stringentconditions can involve hybridization to filter-bound DNA in 6× sodiumchloride/sodium citrate (SSC) at about 45° C. followed by one or morewashes in 0.2×SSC/0.1% SDS at about 50-65° C.; hybridization underhighly stringent conditions can involve hybridization to filter-boundnucleic acid in 6×SSC at about 45° C. followed by one or more washes in0.1×SSC/0.2% SDS at about 68° C. Hybridization under other stringenthybridization conditions are known to those of skill in the art and havebeen described, see, for example, Ausubel F M et al., eds., (1989)Current Protocols in Molecular Biology, Vol. I, Green PublishingAssociates, Inc. and John Wiley & Sons, Inc., New York at pages6.3.1-6.3.6 and 2.10.3.

5.3.2 Cells and Vectors

In certain aspects, provided herein are cells (e.g., host cells)expressing (e.g., recombinantly) antibodies described herein whichspecifically bind to OX40 (e.g., human OX40) and related polynucleotidesand expression vectors. Provided herein are vectors (e.g., expressionvectors) comprising polynucleotides comprising nucleotide sequencesencoding anti-OX40 antibodies or a fragment for recombinant expressionin host cells, preferably in mammalian cells. Also provided herein arehost cells comprising such vectors for recombinantly expressinganti-OX40 antibodies described herein (e.g., human or humanizedantibody). In a particular aspect, provided herein are methods forproducing an antibody described herein, comprising expressing suchantibody in a host cell.

Recombinant expression of an antibody or fragment thereof describedherein (e.g., a heavy or light chain of an antibody described herein)that specifically binds to OX40 (e.g., human OX40) involves constructionof an expression vector containing a polynucleotide that encodes theantibody or fragment. Once a polynucleotide encoding an antibody orfragment thereof (e.g., heavy or light chain variable domains) describedherein has been obtained, the vector for the production of the antibodymolecule can be produced by recombinant DNA technology using techniqueswell known in the art. Thus, methods for preparing a protein byexpressing a polynucleotide containing an antibody or antibody fragment(e.g., light chain or heavy chain) encoding nucleotide sequence aredescribed herein. Methods which are well known to those skilled in theart can be used to construct expression vectors containing antibody orantibody fragment (e.g., light chain or heavy chain) coding sequencesand appropriate transcriptional and translational control signals. Thesemethods include, for example, in vitro recombinant DNA techniques,synthetic techniques, and in vivo genetic recombination. Also providedare replicable vectors comprising a nucleotide sequence encoding anantibody molecule described herein, a heavy or light chain of anantibody, a heavy or light chain variable domain of an antibody or afragment thereof, or a heavy or light chain CDR, operably linked to apromoter. Such vectors can, for example, include the nucleotide sequenceencoding the constant region of the antibody molecule (see, e.g.,International Publication Nos. WO 86/05807 and WO 89/01036; and U.S.Pat. No. 5,122,464) and variable domains of the antibody can be clonedinto such a vector for expression of the entire heavy, the entire lightchain, or both the entire heavy and light chains.

An expression vector can be transferred to a cell (e.g., host cell) byconventional techniques and the resulting cells can then be cultured byconventional techniques to produce an antibody described herein (e.g.,an antibody comprising the CDRs of pab1949 or pab2044) or a fragmentthereof. Thus, provided herein are host cells containing apolynucleotide encoding an antibody described herein (e.g., an antibodycomprising the CDRs of pab1949 or pab2044) or fragments thereof (e.g., aheavy or light chain thereof, or fragment thereof), operably linked to apromoter for expression of such sequences in the host cell. In certainembodiments, for the expression of double-chained antibodies, vectorsencoding both the heavy and light chains, individually, can beco-expressed in the host cell for expression of the entireimmunoglobulin molecule, as detailed below. In certain embodiments, ahost cell contains a vector comprising a polynucleotide encoding boththe heavy chain and light chain of an antibody described herein (e.g.,an antibody comprising the CDRs of pab1949 or pab2044), or a fragmentthereof. In specific embodiments, a host cell contains two differentvectors, a first vector comprising a polynucleotide encoding a heavychain or a heavy chain variable region of an antibody described herein(e.g., an antibody comprising the CDRs of pab1949 or pab2044), or afragment thereof, and a second vector comprising a polynucleotideencoding a light chain or a light chain variable region of an antibodydescribed herein (e.g., an antibody comprising the CDRs of pab1949 orpab2044), or a fragment thereof. In other embodiments, a first host cellcomprises a first vector comprising a polynucleotide encoding a heavychain or a heavy chain variable region of an antibody described herein(e.g., an antibody comprising the CDRs of pab1949 or pab2044), or afragment thereof, and a second host cell comprises a second vectorcomprising a polynucleotide encoding a light chain or a light chainvariable region of an antibody described herein (e.g., an antibodycomprising the CDRs of pab1949 or pab2044). In specific embodiments, aheavy chain/heavy chain variable region expressed by a first cellassociated with a light chain/light chain variable region of a secondcell to form an anti-OX40 antibody described herein (e.g., antibodycomprising the CDRs pab1949 or pab2044). In certain embodiments,provided herein is a population of host cells comprising such first hostcell and such second host cell.

In a particular embodiment, provided herein is a population of vectorscomprising a first vector comprising a polynucleotide encoding a lightchain/light chain variable region of an anti-OX40 antibody describedherein (e.g., antibody comprising the CDRs of pab1949 or pab2044), and asecond vector comprising a polynucleotide encoding a heavy chain/heavychain variable region of an anti-OX40 antibody described herein (e.g.,antibody comprising the CDRs of pab1949 or pab2044).

A variety of host-expression vector systems can be utilized to expressantibody molecules described herein (e.g., an antibody comprising theCDRs of pab1949 or pab2044) (see, e.g., U.S. Pat. No. 5,807,715). Suchhost-expression systems represent vehicles by which the coding sequencesof interest can be produced and subsequently purified, but alsorepresent cells which can, when transformed or transfected with theappropriate nucleotide coding sequences, express an antibody moleculedescribed herein in situ. These include but are not limited tomicroorganisms such as bacteria (e.g., E. coli and B. subtilis)transformed with recombinant bacteriophage DNA, plasmid DNA or cosmidDNA expression vectors containing antibody coding sequences; yeast(e.g., Saccharomyces Pichia) transformed with recombinant yeastexpression vectors containing antibody coding sequences; insect cellsystems infected with recombinant virus expression vectors (e.g.,baculovirus) containing antibody coding sequences; plant cell systems(e.g., green algae such as Chlamydomonas reinhardtii) infected withrecombinant virus expression vectors (e.g., cauliflower mosaic virus,CaMV; tobacco mosaic virus, TMV) or transformed with recombinant plasmidexpression vectors (e.g., Ti plasmid) containing antibody codingsequences; or mammalian cell systems (e.g., COS (e.g., COS1 or COS),CHO, BHK, MDCK, HEK 293, NS0, PER.C6, VERO, CRL7O3O, HsS78Bst, HeLa, andNIH 3T3, HEK-293T, HepG2, SP210, R1.1, B-W, L-M, BSC1, BSC40, YB/20 andBMT10 cells) harboring recombinant expression constructs containingpromoters derived from the genome of mammalian cells (e.g.,metallothionein promoter) or from mammalian viruses (e.g., theadenovirus late promoter; the vaccinia virus 7.5K promoter). In aspecific embodiment, cells for expressing antibodies described herein(e.g., an antibody comprising the CDRs of any one of antibodies pab1949or pab2044) are CHO cells, for example CHO cells from the CHO GS System™(Lonza). In a particular embodiment, cells for expressing antibodiesdescribed herein are human cells, e.g., human cell lines. In a specificembodiment, a mammalian expression vector is pOptiVEC™ or pcDNA3.3. In aparticular embodiment, bacterial cells such as Escherichia coli, oreukaryotic cells (e.g., mammalian cells), especially for the expressionof whole recombinant antibody molecule, are used for the expression of arecombinant antibody molecule. For example, mammalian cells such asChinese hamster ovary (CHO) cells in conjunction with a vector such asthe major intermediate early gene promoter element from humancytomegalovirus is an effective expression system for antibodies(Foecking M K & Hofstetter H (1986) Gene 45: 101-105; and Cockett M I etal., (1990) Biotechnology 8: 662-667). In certain embodiments,antibodies described herein are produced by CHO cells or NS0 cells. In aspecific embodiment, the expression of nucleotide sequences encodingantibodies described herein which immunospecifically bind OX40 (e.g.,human OX40) is regulated by a constitutive promoter, inducible promoteror tissue specific promoter.

In bacterial systems, a number of expression vectors can beadvantageously selected depending upon the use intended for the antibodymolecule being expressed. For example, when a large quantity of such anantibody is to be produced, for the generation of pharmaceuticalcompositions of an antibody molecule, vectors which direct theexpression of high levels of fusion protein products that are readilypurified can be desirable. Such vectors include, but are not limited to,the E. coli expression vector pUR278 (Ruether U & Mueller-Hill B (1983)EMBO J 2: 1791-1794), in which the antibody coding sequence can beligated individually into the vector in frame with the lac Z codingregion so that a fusion protein is produced; pIN vectors (Inouye S &Inouye M (1985) Nuc Acids Res 13: 3101-3109; Van Heeke G & Schuster S M(1989) J Biol Chem 24: 5503-5509); and the like. For example, pGEXvectors can also be used to express foreign polypeptides as fusionproteins with glutathione 5-transferase (GST). In general, such fusionproteins are soluble and can easily be purified from lysed cells byadsorption and binding to matrix glutathione agarose beads followed byelution in the presence of free glutathione. The pGEX vectors aredesigned to include thrombin or factor Xa protease cleavage sites sothat the cloned target gene product can be released from the GST moiety.

In an insect system, Autographa californica nuclear polyhedrosis virus(AcNPV), for example, can be used as a vector to express foreign genes.The virus grows in Spodoptera frugiperda cells. The antibody codingsequence can be cloned individually into non-essential regions (forexample the polyhedrin gene) of the virus and placed under control of anAcNPV promoter (for example the polyhedrin promoter).

In mammalian host cells, a number of viral-based expression systems canbe utilized. In cases where an adenovirus is used as an expressionvector, the antibody coding sequence of interest can be ligated to anadenovirus transcription/translation control complex, e.g., the latepromoter and tripartite leader sequence. This chimeric gene can then beinserted in the adenovirus genome by in vitro or in vivo recombination.Insertion in a non-essential region of the viral genome (e.g., region E1or E3) will result in a recombinant virus that is viable and capable ofexpressing the antibody molecule in infected hosts (e.g., see Logan J &Shenk T (1984) PNAS 81: 3655-3659). Specific initiation signals can alsobe required for efficient translation of inserted antibody codingsequences. These signals include the ATG initiation codon and adjacentsequences. Furthermore, the initiation codon must be in phase with thereading frame of the desired coding sequence to ensure translation ofthe entire insert. These exogenous translational control signals andinitiation codons can be of a variety of origins, both natural andsynthetic. The efficiency of expression can be enhanced by the inclusionof appropriate transcription enhancer elements, transcriptionterminators, etc. (see, e.g., Bitter G et al., (1987) Methods Enzymol153: 516-544).

In addition, a host cell strain can be chosen which modulates theexpression of the inserted sequences, or modifies and processes the geneproduct in the specific fashion desired. Such modifications (e.g.,glycosylation) and processing (e.g., cleavage) of protein products canbe important for the function of the protein. Different host cells havecharacteristic and specific mechanisms for the post-translationalprocessing and modification of proteins and gene products. Appropriatecell lines or host systems can be chosen to ensure the correctmodification and processing of the foreign protein expressed. To thisend, eukaryotic host cells which possess the cellular machinery forproper processing of the primary transcript, glycosylation, andphosphorylation of the gene product can be used. Such mammalian hostcells include but are not limited to CHO, VERO, BHK, Hela, MDCK, HEK293, NIH 3T3, W138, BT483, Hs578T, HTB2, BT2O and T47D, NS0 (a murinemyeloma cell line that does not endogenously produce any immunoglobulinchains), CRL7O3O, COS (e.g., COS1 or COS), PER.C6, VERO, HsS78Bst,HEK-293T, HepG2, SP210, R1.1, B-W, L-M, BSC1, BSC40, YB/20, BMT10 andHsS78Bst cells. In certain embodiments, anti-OX40 antibodies describedherein (e.g., an antibody comprising the CDRs of pab1949 or pab2044) areproduced in mammalian cells, such as CHO cells.

In a specific embodiment, the antibodies described herein have reducedfucose content or no fucose content. Such antibodies can be producedusing techniques known one skilled in the art. For example, theantibodies can be expressed in cells deficient or lacking the ability ofto fucosylate. In a specific example, cell lines with a knockout of bothalleles of α1,6-fucosyltransferase can be used to produce antibodieswith reduced fucose content. The Potelligent® system (Lonza) is anexample of such a system that can be used to produce antibodies withreduced fucose content.

For long-term, high-yield production of recombinant proteins, stableexpression cells can be generated. For example, cell lines which stablyexpress an anti-OX40 antibody described herein (e.g., an antibodycomprising the CDRs of pab1949 or pab2044) can be engineered. Inspecific embodiments, a cell provided herein stably expresses a lightchain/light chain variable domain and a heavy chain/heavy chain variabledomain which associate to form an antibody described herein (e.g., anantibody comprising the CDRs of pab1949 or pab2044).

In certain aspects, rather than using expression vectors which containviral origins of replication, host cells can be transformed with DNAcontrolled by appropriate expression control elements (e.g., promoter,enhancer, sequences, transcription terminators, polyadenylation sites,etc.), and a selectable marker. Following the introduction of theforeign DNA/polynucleotide, engineered cells can be allowed to grow for1-2 days in an enriched media, and then are switched to a selectivemedia. The selectable marker in the recombinant plasmid confersresistance to the selection and allows cells to stably integrate theplasmid into their chromosomes and grow to form foci which in turn canbe cloned and expanded into cell lines. This method can advantageouslybe used to engineer cell lines which express an anti-OX40 antibodydescribed herein or a fragment thereof. Such engineered cell lines canbe particularly useful in screening and evaluation of compositions thatinteract directly or indirectly with the antibody molecule.

A number of selection systems can be used, including but not limited to,the herpes simplex virus thymidine kinase (Wigler M et al., (1977) Cell11(1): 223-232), hypoxanthineguanine phosphoribosyltransferase(Szybalska E H & Szybalski W (1962) PNAS 48(12): 2026-2034) and adeninephosphoribosyltransferase (Lowy I et al., (1980) Cell 22(3): 817-823)genes can be employed in tk-, hgprt- or aprt-cells, respectively. Also,antimetabolite resistance can be used as the basis of selection for thefollowing genes: dhfr, which confers resistance to methotrexate (WiglerM et al., (1980) PNAS 77(6): 3567-3570; O'Hare K et al., (1981) PNAS 78:1527-1531); gpt, which confers resistance to mycophenolic acid (MulliganR C & Berg P (1981) PNAS 78(4): 2072-2076); neo, which confersresistance to the aminoglycoside G-418 (Wu G Y & Wu C H (1991)Biotherapy 3: 87-95; Tolstoshev P (1993) Ann Rev Pharmacol Toxicol 32:573-596; Mulligan R C (1993) Science 260: 926-932; and Morgan R A &Anderson W F (1993) Ann Rev Biochem 62: 191-217; Nabel G J & Felgner P L(1993) Trends Biotechnol 11(5): 211-215); and hygro, which confersresistance to hygromycin (Santerre R F et al., (1984) Gene 30(1-3):147-156). Methods commonly known in the art of recombinant DNAtechnology can be routinely applied to select the desired recombinantclone and such methods are described, for example, in Ausubel F M etal., (eds.), Current Protocols in Molecular Biology, John Wiley & Sons,N Y (1993); Kriegler M, Gene Transfer and Expression, A LaboratoryManual, Stockton Press, N Y (1990); and in Chapters 12 and 13, DracopoliN C et al., (eds.), Current Protocols in Human Genetics, John Wiley &Sons, N Y (1994); Colbère-Garapin F et al., (1981) J Mol Biol 150: 1-14,which are incorporated by reference herein in their entireties.

The expression levels of an antibody molecule can be increased by vectoramplification (for a review, see Bebbington C R & Hentschel C C G, Theuse of vectors based on gene amplification for the expression of clonedgenes in mammalian cells in DNA cloning, Vol. 3 (Academic Press, NewYork, 1987)). When a marker in the vector system expressing antibody isamplifiable, increase in the level of inhibitor present in culture ofhost cell will increase the number of copies of the marker gene. Sincethe amplified region is associated with the antibody gene, production ofthe antibody will also increase (Crouse G F et al., (1983) Mol Cell Biol3: 257-66).

The host cell can be co-transfected with two or more expression vectorsdescribed herein, the first vector encoding a heavy chain derivedpolypeptide and the second vector encoding a light chain derivedpolypeptide. The two vectors can contain identical selectable markerswhich enable equal expression of heavy and light chain polypeptides. Thehost cells can be co-transfected with different amounts of the two ormore expression vectors. For example, host cells can be transfected withany one of the following ratios of a first expression vector and asecond expression vector: 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9,1:10, 1:12, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, or 1:50.

Alternatively, a single vector can be used which encodes, and is capableof expressing, both heavy and light chain polypeptides. In suchsituations, the light chain should be placed before the heavy chain toavoid an excess of toxic free heavy chain (Proudfoot N.J. (1986) Nature322: 562-565; and Köhler G (1980) PNAS 77: 2197-2199). The codingsequences for the heavy and light chains can comprise cDNA or genomicDNA. The expression vector can be monocistronic or multicistronic. Amulticistronic nucleic acid construct can encode 2, 3, 4, 5, 6, 7, 8, 9,10 or more, or in the range of 2-5, 5-10 or 10-20 genes/nucleotidesequences. For example, a bicistronic nucleic acid construct cancomprise in the following order a promoter, a first gene (e.g., heavychain of an antibody described herein), and a second gene and (e.g.,light chain of an antibody described herein). In such an expressionvector, the transcription of both genes can be driven by the promoter,whereas the translation of the mRNA from the first gene can be by acap-dependent scanning mechanism and the translation of the mRNA fromthe second gene can be by a cap-independent mechanism, e.g., by an IRES.

Once an antibody molecule described herein has been produced byrecombinant expression, it can be purified by any method known in theart for purification of an immunoglobulin molecule, for example, bychromatography (e.g., ion exchange, affinity, particularly by affinityfor the specific antigen after Protein A, and sizing columnchromatography), centrifugation, differential solubility, or by anyother standard technique for the purification of proteins. Further, theantibodies described herein can be fused to heterologous polypeptidesequences described herein or otherwise known in the art to facilitatepurification.

In specific embodiments, an antibody described herein is isolated orpurified. Generally, an isolated antibody is one that is substantiallyfree of other antibodies with different antigenic specificities than theisolated antibody. For example, in a particular embodiment, apreparation of an antibody described herein is substantially free ofcellular material and/or chemical precursors. The language“substantially free of cellular material” includes preparations of anantibody in which the antibody is separated from cellular components ofthe cells from which it is isolated or recombinantly produced. Thus, anantibody that is substantially free of cellular material includespreparations of antibody having less than about 30%, 20%, 10%, 5%, 2%,1%, 0.5%, or 0.1% (by dry weight) of heterologous protein (also referredto herein as a “contaminating protein”) and/or variants of an antibody,for example, different post-translational modified forms of an antibody.When the antibody or fragment is recombinantly produced, it is alsogenerally substantially free of culture medium, i.e., culture mediumrepresents less than about 20%, 10%, 2%, 1%, 0.5%, or 0.1% of the volumeof the protein preparation. When the antibody or fragment is produced bychemical synthesis, it is generally substantially free of chemicalprecursors or other chemicals, i.e., it is separated from chemicalprecursors or other chemicals which are involved in the synthesis of theprotein. Accordingly, such preparations of the antibody or fragment haveless than about 30%, 20%, 10%, or 5% (by dry weight) of chemicalprecursors or compounds other than the antibody or fragment of interest.In a specific embodiment, antibodies described herein are isolated orpurified.

5.4 Pharmaceutical Compositions

Provided herein are compositions comprising an antibody described hereinhaving the desired degree of purity in a physiologically acceptablecarrier, excipient or stabilizer (Remington's Pharmaceutical Sciences(1990) Mack Publishing Co., Easton, Pa.). Acceptable carriers,excipients, or stabilizers are nontoxic to recipients at the dosages andconcentrations employed.

Pharmaceutical compositions described herein can be useful in enhancing,inducing, or activating an OX40 activity and treating a condition, suchas cancer or an infectious disease. Examples of cancer that can betreated in accordance with the methods described herein include, but arenot limited to, B cell lymphomas (e.g., B cell chronic lymphocyticleukemia, B cell non-Hodgkin lymphoma, cutaneous B cell lymphoma,diffuse large B cell lymphoma), basal cell carcinoma, bladder cancer,blastoma, brain metastasis, breast cancer, Burkitt lymphoma, carcinoma(e.g., adenocarcinoma (e.g., of the gastroesophageal junction)),cervical cancer, colon cancer, colorectal cancer (colon cancer andrectal cancer), endometrial carcinoma, esophageal cancer, Ewing sarcoma,follicular lymphoma, gastric cancer, gastroesophageal junctioncarcinoma, gastrointestinal cancer, glioblastoma (e.g., glioblastomamultiforme, e.g., newly diagnosed or recurrent), glioma, head and neckcancer (e.g., head and neck squamous cell carcinoma), hepaticmetastasis, Hodgkin's and non-Hodgkin's lymphoma, kidney cancer (e.g.,renal cell carcinoma and Wilms' tumors), laryngeal cancer, leukemia(e.g., chronic myelocytic leukemia, hairy cell leukemia), liver cancer(e.g., hepatic carcinoma and hepatoma), lung cancer (e.g., non-smallcell lung cancer and small-cell lung cancer), lymphblastic lymphoma,lymphoma, mantle cell lymphoma, metastatic brain tumor, metastaticcancer, myeloma (e.g., multiple myeloma), neuroblastoma, ocularmelanoma, oropharyngeal cancer, osteosarcoma, ovarian cancer, pancreaticcancer (e.g., pancreatis ductal adenocarcinoma), prostate cancer (e.g.,hormone refractory (e.g., castration resistant), metastatic, metastatichormone refractory (e.g., castration resistant, androgen independent)),renal cell carcinoma (e.g., metastatic), salivary gland carcinoma,sarcoma (e.g., rhabdomyosarcoma), skin cancer (e.g., melanoma (e.g.,metastatic melanoma)), soft tissue sarcoma, solid tumor, squamous cellcarcinoma, synovia sarcoma, testicular cancer, thyroid cancer,transitional cell cancer (urothelial cell cancer), uveal melanoma (e.g.,metastatic), verrucous carcinoma, vulval cancer, and Waldenstrommacroglobulinemia. In one embodiment, examples of cancer that can betreated in accordance with the methods described herein include, but arenot limited to, advanced, recurrent, or metastatic solid tumor, lymphoma(e.g., diffuse large B-cell lymphoma or burkitt's lymphoma), breastcancer, prostate cancer, head & neck cancer, colorectal cancer, coloncancer, melanoma (e.g., metastatic melanoma), endometrial cancer, renalcell carcinoma, renal clear cell carcinoma, lung cancer (e.g., non-smallcell lung cancer or lung adenocarcinoma), ovarian cancer, gastriccancer, bladder cancer, stomach cancer, uterine cancer,pheochromocytoma, metastatic cutaneous squamous cell carcinoma (e.g., intransplantation patients), merkel cell carcinoma, cutaneous T-celllymphoma, neuro-endocrine tumor, tumor of bone origin (e.g.,osteosarcoma), hemangiopericytoma, tumor related to genetic syndromes(NF1 or VHL), chordoma, ependymoma, medulloblastoma, germinoma, tumor ofsmall intestine, appendiceal cancer, and viral related tumor (e.g.,Kaposi's sarcoma). The pharmaceutical compositions described herein arein one embodiment for use as a medicament or diagnostic. Thepharmaceutical compositions that comprise an agonistic antibodydescribed herein are in one embodiment for use in a method for thetreatment of cancer.

Pharmaceutical compositions described herein that comprise anantagonistic antibody described herein can be useful in reducing,inhibiting, or deactivating an OX40 activity and treating a condition,such as an inflammatory or autoimmune disease or disorder or aninfectious disease. The pharmaceutical compositions that comprise anantagonistic antibody described herein are in one embodiment for use ina method for the treatment of an inflammatory or autoimmune disease ordisorder or an infectious disease.

Pharmaceutical compositions described herein that comprise anantagonistic antibody described herein can be useful in reducing,deactivating, or inhibiting an OX40 activity and treating a conditionselected from the group consisting of infections (viral, bacterial,fungal and parasitic), endotoxic shock associated with infection,arthritis, rheumatoid arthritis, asthma, chronic obstructive pulmonarydisease (COPD), pelvic inflammatory disease, Alzheimer's Disease,inflammatory bowel disease, Crohn's disease, ulcerative colitis,Peyronie's Disease, coeliac disease, gallbladder disease, Pilonidaldisease, peritonitis, psoriasis, vasculitis, surgical adhesions, stroke,Type I Diabetes, lyme disease, arthritis, meningoencephalitis, uveitis,autoimmune uveitis, immune mediated inflammatory disorders of thecentral and peripheral nervous system such as multiple sclerosis, lupus(such as systemic lupus erythematosus) and Guillain-Barr syndrome,dermatitis, atopic dermatitis, autoimmune hepatitis, fibrosingalveolitis, Grave's disease, IgA nephropathy, idiopathicthrombocytopenic purpura, Meniere's disease, pemphigus, primary biliarycirrhosis, sarcoidosis, scleroderma, Wegener's granulomatosis,pancreatitis, trauma (surgery), graft-versus-host disease, transplantrejection, heart disease (i.e., cardiovascular disease) includingischaemic diseases such as myocardial infarction as well asatherosclerosis, intravascular coagulation, bone resorption,osteoporosis, osteoarthritis, periodontitis, hypochlorhydia,neuromyelitis optica, celiac disease, connective tissue disorder (e.g.,lupus), post infectious inflammatory disorder (e.g., Guillain-Barresyndrome), and paraneoplastic syndromes.

The compositions to be used for in vivo administration can be sterile.This is readily accomplished by filtration through, e.g., sterilefiltration membranes.

5.5 Uses and Methods

5.5.1 Therapeutic Uses and Methods

In one aspect, presented herein are methods for modulating one or moreimmune functions or responses in a subject, comprising to a subject inneed thereof administering an anti-OX40 antibody described herein, or acomposition thereof. In a specific aspect, presented herein are methodsfor activating, enhancing or inducing one or more immune functions orresponses in a subject, comprising to a subject in need thereofadministering an anti-OX40 antibody or a composition thereof. In aspecific embodiment, presented herein are methods for preventing and/ortreating diseases in which it is desirable to activate or enhance one ormore immune functions or responses, comprising administering to asubject in need thereof an anti-OX40 antibody described herein or acomposition thereof. In a certain embodiment, presented herein aremethods of treating an infectious disease comprising administering to asubject in need thereof an anti-OX40 antibody or a composition thereof.In a certain embodiment, presented herein are methods of treating cancercomprising administering to a subject in need thereof an anti-OX40antibody or a composition thereof. The cancer can be selected from agroup consisting of melanoma, renal cancer, and prostate cancer. Thecancer can be selected from a group consisting of melanoma, renalcancer, prostate cancer, colon cancer, and lung cancer. In a certainembodiment, presented herein are methods of treating melanoma comprisingadministering to a subject in need thereof an anti-OX40 antibody or acomposition thereof. In a certain embodiment, presented herein aremethods of treating renal cancer comprising administering to a subjectin need thereof an anti-OX40 antibody or a composition thereof. In acertain embodiment, presented herein are methods of treating prostatecancer comprising administering to a subject in need thereof ananti-OX40 antibody or a composition thereof. In certain embodiments,presented herein are methods of treating colon cancer comprisingadministering to a subject in need thereof an anti-OX40 antibody or acomposition thereof. In certain embodiments, presented herein aremethods of treating lung cancer comprising administering to a subject inneed thereof an anti-OX40 antibody or a composition thereof. In certainembodiments, presented herein are methods of treating non-small celllung cancer (NSCLC) comprising administering to a subject in needthereof an anti-OX40 antibody or a composition thereof. In one instance,the method further comprises administering to the subject a checkpointtargeting agent. In one instance, the checkpoint targeting agent isselected from the group consisting of an antagonist anti-PD-1 antibody,an antagonist anti-PD-L1 antibody, an antagonist anti-PD-L2 antibody, anantagonist anti-CTLA-4 antibody, an antagonist anti-TIM-3 antibody, anantagonist anti-LAG-3 antibody, an antagonist anti-CEACAM1 antibody, anagonist anti-GITR antibody, an agonist anti-CD137 antibody, and anagonist anti-OX40 antibody. In certain embodiments, the checkpointtargeting agent is an antagonist anti-PD-1 antibody. In certainembodiments, the checkpoint targeting agent is an antagonist anti-PD-L1antibody. In certain embodiments, the checkpoint targeting agent is anagonist anti-GITR antibody. In certain embodiments, the checkpointtargeting agent is an agonist anti-CD137 antibody.

In certain embodiments, an anti-PD-1 antibody is used in methodsdisclosed herein. In certain embodiments, the anti-PD-1 antibody isNivolumab, also known as BMS-936558 or MDX1106, developed byBristol-Myers Squibb. In certain embodiments, the anti-PD-1 antibody isPembrolizumab, also known as Lambrolizumab or MK-3475, developed byMerck & Co. In certain embodiments, the anti-PD-1 antibody isPidilizumab, also known as CT-011, developed by CureTech. In certainembodiments, the anti-PD-1 antibody is MEDI0680, also known as AMP-514,developed by Medimmune. In certain embodiments, the anti-PD-1 antibodyis PDR001 developed by Novartis Pharmaceuticals. In certain embodiments,the anti-PD-1 antibody is REGN2810 developed by RegeneronPharmaceuticals. In certain embodiments, the anti-PD-1 antibody isPF-06801591 developed by Pfizer. In certain embodiments, the anti-PD-1antibody is BGB-A317 developed by BeiGene. In certain embodiments, theanti-PD-1 antibody is TSR-042 developed by AnaptysBio and Tesaro. Incertain embodiments, the anti-PD-1 antibody is SHR-1210 developed byHengrui.

Further non-limiting examples of anti-PD-1 antibodies that may be usedin treatment methods disclosed herein are disclosed in the followingpatents and patent applications, which are incorporated herein byreference in their entireties for all purposes: U.S. Pat. Nos.6,808,710; 7,332,582; 7,488,802; 8,008,449; 8,114,845; 8,168,757;8,354,509; 8,686,119; 8,735,553; 8,747,847; 8,779,105; 8,927,697;8,993,731; 9,102,727; 9,205,148; U.S. Publication No. US 2013/0202623A1; U.S. Publication No. US 2013/0291136 A1; U.S. Publication No. US2014/0044738 A1; U.S. Publication No. US 2014/0356363 A1; U.S.Publication No. US 2016/0075783 A1; and PCT Publication No. WO2013/033091 A1; PCT Publication No. WO 2015/036394 A1; PCT PublicationNo. WO 2014/179664 A2; PCT Publication No. WO 2014/209804 A1; PCTPublication No. WO 2014/206107 A1; PCT Publication No. WO 2015/058573A1; PCT Publication No. WO 2015/085847 A1; PCT Publication No. WO2015/200119 A1; PCT Publication No. WO 2016/015685 A1; and PCTPublication No. WO 2016/020856 A1.

In certain embodiments, an anti-PD-L1 antibody is used in methodsdisclosed herein. In certain embodiments, the anti-PD-L1 antibody isatezolizumab developed by Genentech. In certain embodiments, theanti-PD-L1 antibody is durvalumab developed by AstraZeneca, Celgene andMedimmune. In certain embodiments, the anti-PD-L1 antibody is avelumab,also known as MSB0010718C, developed by Merck Serono and Pfizer. Incertain embodiments, the anti-PD-L1 antibody is MDX-1105 developed byBristol-Myers Squibb. In certain embodiments, the anti-PD-L1 antibody isAMP-224 developed by Amplimmune and GSK.

Non-limiting examples of anti-PD-L1 antibodies that may be used intreatment methods disclosed herein are disclosed in the followingpatents and patent applications, which are incorporated herein byreference in their entireties for all purposes: U.S. Pat. Nos.7,943,743; 8,168,179; 8,217,149; 8,552,154; 8,779,108; 8,981,063;9,175,082; U.S. Publication No. US 2010/0203056 A1; U.S. Publication No.US 2003/0232323 A1; U.S. Publication No. US 2013/0323249 A1; U.S.Publication No. US 2014/0341917 A1; U.S. Publication No. US 2014/0044738A1; U.S. Publication No. US 2015/0203580 A1; U.S. Publication No. US2015/0225483 A1; U.S. Publication No. US 2015/0346208 A1; U.S.Publication No. US 2015/0355184 A1; and PCT Publication No. WO2014/100079 A1; PCT Publication No. WO 2014/022758 A1; PCT PublicationNo. WO 2014/055897 A2; PCT Publication No. WO 2015/061668 A1; PCTPublication No. WO 2015/109124 A1; PCT Publication No. WO 2015/195163A1; PCT Publication No. WO 2016/000619 A1; and PCT Publication No. WO2016/030350 A1.

In a certain embodiment, presented herein are methods of treating acancer selected from the group consisting of: B cell lymphomas (e.g., Bcell chronic lymphocytic leukemia, B cell non-Hodgkin lymphoma,cutaneous B cell lymphoma, diffuse large B cell lymphoma), basal cellcarcinoma, bladder cancer, blastoma, brain metastasis, breast cancer,Burkitt lymphoma, carcinoma (e.g., adenocarcinoma (e.g., of thegastroesophageal junction)), cervical cancer, colon cancer, colorectalcancer (colon cancer and rectal cancer), endometrial carcinoma,esophageal cancer, Ewing sarcoma, follicular lymphoma, gastric cancer,gastroesophageal junction carcinoma, gastrointestinal cancer,glioblastoma (e.g., glioblastoma multiforme, e.g., newly diagnosed orrecurrent), glioma, head and neck cancer (e.g., head and neck squamouscell carcinoma), hepatic metastasis, Hodgkin's and non-Hodgkin'slymphoma, kidney cancer (e.g., renal cell carcinoma and Wilms' tumors),laryngeal cancer, leukemia (e.g., chronic myelocytic leukemia, hairycell leukemia), liver cancer (e.g., hepatic carcinoma and hepatoma),lung cancer (e.g., non-small cell lung cancer and small-cell lungcancer), lymphblastic lymphoma, lymphoma, mantle cell lymphoma,metastatic brain tumor, metastatic cancer, myeloma (e.g., multiplemyeloma), neuroblastoma, ocular melanoma, oropharyngeal cancer,osteosarcoma, ovarian cancer, pancreatic cancer (e.g., pancreatis ductaladenocarcinoma), prostate cancer (e.g., hormone refractory (e.g.,castration resistant), metastatic, metastatic hormone refractory (e.g.,castration resistant, androgen independent)), renal cell carcinoma(e.g., metastatic), salivary gland carcinoma, sarcoma (e.g.,rhabdomyosarcoma), skin cancer (e.g., melanoma (e.g., metastaticmelanoma)), soft tissue sarcoma, solid tumor, squamous cell carcinoma,synovia sarcoma, testicular cancer, thyroid cancer, transitional cellcancer (urothelial cell cancer), uveal melanoma (e.g., metastatic),verrucous carcinoma, vulval cancer, and Waldenstrom macroglobulinemia.In a certain embodiment, presented herein are methods of treating acancer selected from the group consisting of: advanced, recurrent, ormetastatic solid tumor, lymphoma (e.g., diffuse large B-cell lymphoma orburkitt's lymphoma), breast cancer, prostate cancer, head & neck cancer,colorectal cancer, colon cancer, melanoma (e.g., metastatic melanoma),endometrial cancer, renal cell carcinoma, renal clear cell carcinoma,lung cancer (e.g., non-small cell lung cancer or lung adenocarcinoma),ovarian cancer, gastric cancer, bladder cancer, stomach cancer, uterinecancer, pheochromocytoma, metastatic cutaneous squamous cell carcinoma(e.g., in transplantation patients), merkel cell carcinoma, cutaneousT-cell lymphoma, neuro-endocrine tumor, tumor of bone origin (e.g.,osteosarcoma), hemangiopericytoma, tumor related to genetic syndromes(NF1 or VHL), chordoma, ependymoma, medulloblastoma, germinoma, tumor ofsmall intestine, appendiceal cancer, and viral related tumor (e.g.,Kaposi's sarcoma).

In another embodiment, an anti-OX40 antibody is administered to apatient diagnosed with cancer to increase the proliferation and/oreffector function of one or more immune cell populations (e.g., T celleffector cells, such as CD4⁺ and CD8⁺ T cells) in the patient.

In a specific embodiment, an anti-OX40 antibody described hereinactivates or enhances or induces one or more immune functions orresponses in a subject by at least 99%, at least 98%, at least 95%, atleast 90%, at least 85%, at least 80%, at least 75%, at least 70%, atleast 60%, at least 50%, at least 45%, at least 40%, at least 45%, atleast 35%, at least 30%, at least 25%, at least 20%, or at least 10%, orin the range of between 10% to 25%, 25% to 50%, 50% to 75%, or 75% to95% relative to the immune function in a subject not administered theanti-OX40 antibody described herein using assays well known in the art,e.g., ELISPOT, ELISA, and cell proliferation assays. In a specificembodiment, the immune function is cytokine production (e.g., IL-2,TNF-α, IFN-γ, IL-4, IL-10, and/or IL-13 production). In anotherembodiment, the immune function is T cell proliferation/expansion, whichcan be assayed, e.g., by flow cytometry to detect the number of cellsexpressing markers of T cells (e.g., CD3, CD4, or CD8). In anotherembodiment, the immune function is antibody production, which can beassayed, e.g., by ELISA. In some embodiments, the immune function iseffector function, which can be assayed, e.g., by a cytotoxicity assayor other assays well known in the art. In another embodiment, the immunefunction is a Th1 response. In another embodiment, the immune functionis a Th2 response. In another embodiment, the immune function is amemory response.

In specific embodiments, non-limiting examples of immune functions thatcan be enhanced or induced by an anti-OX40 antibody areproliferation/expansion of effector lymphocytes (e.g., increase in thenumber of effector T lymphocytes), and inhibition of apoptosis ofeffector lymphocytes (e.g., effector T lymphocytes). In particularembodiments, an immune function enhanced or induced by an anti-OX40antibody described herein is proliferation/expansion in the number of oractivation of CD4⁺ T cells (e.g., Th1 and Th2 helper T cells), CD8⁺ Tcells (e.g., cytotoxic T lymphocytes, alpha/beta T cells, andgamma/delta T cells), B cells (e.g., plasma cells), memory T cells,memory B cells, tumor-resident T cells, CD122⁺ T cells, natural killer(NK) cells), macrophages, monocytes, dendritic cells, mast cells,eosinophils, basophils or polymorphonucleated leukocytes. In oneembodiment, an anti-OX40 antibody described herein activates or enhancesthe proliferation/expansion or number of lymphocyte progenitors. In someembodiments, an anti-OX40 antibody described herein increases the numberof CD4⁺ T cells (e.g., Th1 and Th2 helper T cells), CD8⁺ T cells (e.g.,cytotoxic T lymphocytes, alpha/beta T cells, and gamma/delta T cells), Bcells (e.g., plasma cells), memory T cells, memory B cells,tumor-resident T cells, CD122⁺ T cells, natural killer cells (NK cells),macrophages, monocytes, dendritic cells, mast cells, eosinophils,basophils or polymorphonucleated leukocytes by approximately at least99%, at least 98%, at least 95%, at least 90%, at least 85%, at least80%, at least 75%, at least 70%, at least 60%, at least 50%, at least45%, at least 40%, at least 45%, at least 35%, at least 30%, at least25%, at least 20%, or at least 10%, or in the range of between 10% to25%, 25% to 50%, 50% to 75%, or 75% to 95% relative a negative control(e.g., number of the respective cells not treated, cultured, orcontacted with an anti-OX40 antibody described herein).

In some embodiments, an anti-OX40 antibody described herein isadministered to a subject in combination with a compound that targets animmunomodulatory enzyme(s) such as IDO (indoleamine-(2,3)-dioxygenase)and TDO (tryptophan 2,3-dioxygenase). In particular embodiments, suchcompound is selected from the group consisting of epacadostat (IncyteCorp), F001287 (Flexus Biosciences), indoximod (NewLink Genetics), andNLG919 (NewLink Genetics). In one embodiment, the compound isepacadostat. In another embodiment, the compound is F001287. In anotherembodiment, the compound is indoximod. In another embodiment, thecompound is NLG919.

In some embodiments, an anti-OX40 antibody described herein isadministered to a subject in combination with a vaccine.

In some embodiments, an anti-OX40 antibody described herein isadministered to a subject in combination with an anti-CD137 antibody,rituximab, cyclophosphamide, chemotherapy, or radiation therapy.

In some embodiments, an anti-OX40 antibody described herein isadministered to a subject in combination with a heat shock protein basedtumor vaccine or a heat shock protein based pathogen vaccine. In aspecific embodiment, an anti-OX40 antibody is administered to a subjectin combination with a heat shock protein based tumor-vaccine. Heat shockproteins (HSPs) are a family of highly conserved proteins foundubiquitously across all species. Their expression can be powerfullyinduced to much higher levels as a result of heat shock or other formsof stress, including exposure to toxins, oxidative stress or glucosedeprivation. Five families have been classified according to molecularweight: HSP-110, -90, -70, -60 and -28. HSPs deliver immunogenicpeptides through the cross-presentation pathway in antigen presentingcells (APCs) such as macrophages and dendritic cells (DCs), leading to Tcell activation. HSPs function as chaperone carriers of tumor-associatedantigenic peptides forming complexes able to induce tumor-specificimmunity. Upon release from dying tumor cells, the HSP-antigen complexesare taken up by antigen-presenting cells (APCs) wherein the antigens areprocessed into peptides that bind WIC class I and class II moleculesleading to the activation of anti-tumor CD8+ and CD4+ T cells. Theimmunity elicited by HSP complexes derived from tumor preparations isspecifically directed against the unique antigenic peptide repertoireexpressed by the cancer of each subject.

A heat shock protein peptide complex (HSPPC) is a protein peptidecomplex consisting of a heat shock protein non-covalently complexed withantigenic peptides. HSPPCs elicit both innate and adaptive immuneresponses. In a specific embodiment, the antigenic peptide(s) displaysantigenicity for the cancer being treated. HSPPCs are efficiently seizedby APCs via membrane receptors (mainly CD91) or by binding to Toll-likereceptors. HSPPC internalization results in functional maturation of theAPCs with chemokine and cytokine production leading to activation ofnatural killer cells (NK), monocytes and Th1 and Th-2-mediated immuneresponses. In some embodiments, HSPPCs used in methods disclosed hereincomprise one or more heat shock proteins from the hsp60, hsp70, or hsp90family of stress proteins complexed with antigenic peptides. In someembodiments, HSPPCs comprise hsc70, hsp70, hsp90, hsp110, grp170, gp96,calreticulin, or combinations of two or more thereof.

In a specific embodiment, an anti-OX40 antibody is administered to asubject in combination with a heat shock protein peptide complex(HSPPC), e.g., heat shock protein peptide complex-96 (HSPPC-96), totreat cancer. HSPPC-96 comprises a 96 kDa heat shock protein (Hsp),gp96, complexed to antigenic peptides. HSPPC-96 is a cancerimmunotherapy manufactured from a subject's tumor and contains thecancer's antigenic “fingerprint.” In some embodiments, this fingerprintcontains unique antigens that are present only in that particularsubject's specific cancer cells and injection of the vaccine is intendedto stimulate the subject's immune system to recognize and attack anycells with the specific cancer fingerprint.

In some embodiments, the HSPPC, e.g., HSPPC-96, is produced from thetumor tissue of a subject. In a specific embodiment, the HSPPC (e.g.,HSPPC-96) is produced from tumor of the type of cancer or metastatisthereof being treated. In another specific embodiment, the HSPPC (e.g.,HSPPC-96) is autologous to the subject being treated. In someembodiments, the tumor tissue is non-necrotic tumor tissue. In someembodiments, at least 1 gram (e.g., at least 1, at least 2, at least 3,at least 4, at least 5, at least 6, at least 7, at least 8, at least 9,or at least 10 grams) of non-necrotic tumor tissue is used to produce avaccine regimen. In some embodiments, after surgical resection,non-necrotic tumor tissue is frozen prior to use in vaccine preparation.In some embodiments, the HSPPC, e.g., HSPPC-96, is isolated from thetumor tissue by purification techniques, filtered and prepared for aninjectable vaccine. In some embodiments, a subject is administered 6-12doses of the HSPPC, e.g., HSPCC-96. In such embodiments, the HSPPC,e.g., HSPPC-96, doses may be administered weekly for the first 4 dosesand then biweekly for the 2-8 additional doses.

Further examples of HSPPCs that may be used in accordance with themethods described herein are disclosed in the following patents andpatent applications, which are incorporated herein by reference in theirentireties for all purposes, U.S. Pat. Nos. 6,391,306, 6,383,492,6,403,095, 6,410,026, 6,436,404, 6,447,780, 6,447,781 and 6,610,659.

In some embodiment, the present invention relates to an antibody orpharmaceutical composition of the present invention for use as amedicament. In some aspects, the present invention relates to anantibody or pharmaceutical composition of the present invention, for usein a method for the treatment of cancer. In some aspects, the presentinvention relates to an antibody or pharmaceutical composition of thepresent invention, for use in a method for the treatment of cancer in asubject, comprising administering to the subject an effective amount ofan antibody or pharmaceutical composition of the invention. In someaspects, the present invention relates to (a) an antibody orpharmaceutical composition of the present invention and (b) a checkpointtargeting agent, for use as a medicament. In some aspects, the presentinvention relates to (a) an antibody or pharmaceutical composition ofthe present invention and (b) a checkpoint targeting agent, for use in amethod for the treatment of cancer. In some aspects, the presentinvention relates to a composition, kit or kit-of-parts comprising (a)an antibody or pharmaceutical composition of the present invention and(b) a checkpoint targeting agent. In one aspect, the present inventionrelates to (a) an antibody or pharmaceutical composition of the presentinvention and (b) an IDO inhibitor, for use as a medicament. In someaspects, the present invention relates to (a) an antibody orpharmaceutical composition of the present invention and (b) an IDOinhibitor, for use in a method for the treatment of cancer. In someaspects, the present invention relates to a composition, kit orkit-of-parts comprising (a) an antibody or pharmaceutical composition ofthe present invention and (b) an IDO inhibitor. In some aspects, thepresent invention relates to (a) an antibody or pharmaceuticalcomposition of the present invention and (b) a vaccine, for use as amedicament. In some aspects, the present invention relates to (a) anantibody or pharmaceutical composition of the present invention and (b)a vaccine, for use in a method for the treatment of cancer. In someaspects, the present invention relates to a composition, kit orkit-of-parts comprising (a) an antibody or pharmaceutical composition ofthe present invention and (b) a vaccine. In a preferred embodiment of anantibody or pharmaceutical composition for use in a method for thetreatment of cancer, the antibody is agonistic.

In one aspect, the methods for modulating one or more immune functionsor responses in a subject as presented herein are methods fordeactivating, reducing, or inhibiting one or more immune functions orresponses in a subject, comprising to a subject in need thereofadministering an anti-OX40 antagonistic antibody or a compositionthereof. In a specific embodiment, presented herein are methods forpreventing and/or treating diseases in which it is desirable todeactivate, reduce, or inhibit one or more immune functions orresponses, comprising administering to a subject in need thereof ananti-OX40 antagonistic antibody described herein or a compositionthereof. In a certain embodiment, presented herein are methods oftreating an autoimmune or inflammatory disease or disorder comprisingadministering to a subject in need thereof an effective amount of ananti-OX40 antagonistic antibody or a composition thereof. In certainembodiments, the subject is a human. In certain embodiments, the diseaseor disorder is selected from the group consisting of: infections (viral,bacterial, fungal and parasitic), endotoxic shock associated withinfection, arthritis, rheumatoid arthritis, asthma, chronic obstructivepulmonary disease (COPD), pelvic inflammatory disease, Alzheimer'sDisease, inflammatory bowel disease, Crohn's disease, ulcerativecolitis, Peyronie's Disease, coeliac disease, gallbladder disease,Pilonidal disease, peritonitis, psoriasis, vasculitis, surgicaladhesions, stroke, Type I Diabetes, lyme disease, arthritis,meningoencephalitis, uveitis, autoimmune uveitis, immune mediatedinflammatory disorders of the central and peripheral nervous system suchas multiple sclerosis, lupus (such as systemic lupus erythematosus) andGuillain-Barr syndrome, dermatitis, atopic dermatitis, autoimmunehepatitis, fibrosing alveolitis, Grave's disease, IgA nephropathy,idiopathic thrombocytopenic purpura, Meniere's disease, pemphigus,primary biliary cirrhosis, sarcoidosis, scleroderma, Wegener'sgranulomatosis, pancreatitis, trauma (surgery), graft-versus-hostdisease, transplant rejection, heart disease (i.e., cardiovasculardisease) including ischaemic diseases such as myocardial infarction aswell as atherosclerosis, intravascular coagulation, bone resorption,osteoporosis, osteoarthritis, periodontitis, hypochlorhydia,neuromyelitis optica, celiac disease, connective tissue disorders (e.g.,lupus), post infectious inflammatory disorders (e.g., Guillain-Barresyndrome), and paraneoplastic syndromes. In certain embodiments, thedisease or disorder is selected from the group consisting of: transplantrejection, vasculitis, asthma, rheumatoid arthritis, dermatitis,inflammatory bowel disease, uveitis, and lupus. In certain embodiments,any of the methods herein (e.g., methods of treating an infectiousdisease, or methods of treating an autoimmune or inflammatory disease ordisorder) comprise administration to a subject of an antibody asdescribed herein and a checkpoint targeting agent. In certainembodiments, the checkpoint targeting agent is an antibody (e.g., ananti-PD-1 antibody, an anti-PD-L1 antibody, an anti-PD-L2 antibody, ananti-CTLA-4 antibody, an anti-TIM-3 antibody, an anti-LAG-3 antibody, ananti-CEACAM1 antibody, an anti-GITR antibody, an anti-CD137 antibody, oran anti-OX40 antibody). In certain embodiments, the checkpoint targetingagent is an antagonist or agonist antibody. In certain embodiments, thecheckpoint targeting agent is an anti-PD-1 antibody. In certainembodiments, the checkpoint targeting agent is an anti-GITR antibody. Incertain embodiments, the checkpoint targeting agent is an anti-CD137antibody.

In another embodiment, an anti-OX40 antagonistic antibody isadministered to a patient diagnosed with an autoimmune or inflammatorydisease or disorder to decrease the proliferation and/or effectorfunction of one or more immune cell populations (e.g., T cell effectorcells, such as CD4⁺ and CD8⁺ T cells) in the patient.

In a specific embodiment, an anti-OX40 antagonistic antibody describedherein deactivates or reduces or inhibits one or more immune functionsor responses in a subject by at least 99%, at least 98%, at least 95%,at least 90%, at least 85%, at least 80%, at least 75%, at least 70%, atleast 60%, at least 50%, at least 45%, at least 40%, at least 45%, atleast 35%, at least 30%, at least 25%, at least 20%, or at least 10%, orin the range of between 10% to 25%, 25% to 50%, 50% to 75%, or 75% to95% relative to the immune function in a subject not administered theanti-OX40 antagonistic antibody described herein using assays well knownin the art, e.g., ELISPOT, ELISA, and cell proliferation assays. In aspecific embodiment, the immune function is cytokine production (e.g.,IL-2, TNF-α, IFN-γ, IL-4, IL-10, and/or IL-13 production). In anotherembodiment, the immune function is T cell proliferation/expansion, whichcan be assayed, e.g., by flow cytometry to detect the number of cellsexpressing markers of T cells (e.g., CD3, CD4, or CD8). In anotherembodiment, the immune function is antibody production, which can beassayed, e.g., by ELISA. In some embodiments, the immune function iseffector function, which can be assayed, e.g., by a cytotoxicity assayor other assays well known in the art. In another embodiment, the immunefunction is a Th1 response. In another embodiment, the immune functionis a Th2 response. In another embodiment, the immune function is amemory response.

In specific embodiments, non-limiting examples of immune functions thatcan be reduced or inhibited by an anti-OX40 antagonistic antibody areproliferation/expansion of effector lymphocytes (e.g., decrease in thenumber of effector T lymphocytes), and stimulation of apoptosis ofeffector lymphocytes (e.g., effector T lymphocytes). In particularembodiments, an immune function reduced or inhibited by an anti-OX40antagonistic antibody described herein is proliferation/expansion in thenumber of or activation of CD4⁺ T cells (e.g., Th1 and Th2 helper Tcells), CD8⁺ T cells (e.g., cytotoxic T lymphocytes, alpha/beta T cells,and gamma/delta T cells), B cells (e.g., plasma cells), memory T cells,memory B cells, tumor-resident T cells, CD122⁺ T cells, natural killer(NK) cells), macrophages, monocytes, dendritic cells, mast cells,eosinophils, basophils or polymorphonucleated leukocytes. In oneembodiment, an anti-OX40 antagonistic antibody described hereindeactivates or reduces or inhibits the proliferation/expansion or numberof lymphocyte progenitors. In some embodiments, an anti-OX40antagonistic antibody described herein decreases the number of CD4⁺ Tcells (e.g., Th1 and Th2 helper T cells), CD8⁺ T cells (e.g., cytotoxicT lymphocytes, alpha/beta T cells, and gamma/delta T cells), B cells(e.g., plasma cells), memory T cells, memory B cells, tumor-resident Tcells, CD122⁺ T cells, natural killer cells (NK cells), macrophages,monocytes, dendritic cells, mast cells, eosinophils, basophils orpolymorphonucleated leukocytes by approximately at least 99%, at least98%, at least 95%, at least 90%, at least 85%, at least 80%, at least75%, at least 70%, at least 60%, at least 50%, at least 45%, at least40%, at least 45%, at least 35%, at least 30%, at least 25%, at least20%, or at least 10%, or in the range of between 10% to 25%, 25% to 50%,50% to 75%, or 75% to 95% relative a negative control (e.g., number ofthe respective cells not treated, cultured, or contacted with ananti-OX40 antagonistic antibody described herein).

In some aspects, the present invention relates to an antibody orpharmaceutical composition of the present invention, for use in a methodfor the treatment of an autoimmune or inflammatory disease or disorder.In one aspect, the present invention relates to an antibody orpharmaceutical composition of the present invention, for use in a methodfor the treatment of an infectious disease. In a preferred embodiment ofan antibody or pharmaceutical composition for use in a method for thetreatment of an autoimmune or inflammatory disease or disorder, or of aninfectious disease, the antibody is antagonistic.

5.5.1.1 Routes of Administration & Dosage

An antibody or composition described herein can be delivered to asubject by a variety of routes, such as parenteral, subcutaneous,intravenous, intradermal, transdermal, intranasal, intratumoral, andadministration to a tumor draining lymph node. In one embodiment, theantibody or composition is administered by an intravenous orintratumoral route.

The amount of an antibody or composition which will be effective in thetreatment and/or prevention of a condition will depend on the nature ofthe disease, and can be determined by standard clinical techniques.

The precise dose to be employed in a composition will also depend on theroute of administration, and the seriousness of the disease, and shouldbe decided according to the judgment of the practitioner and eachsubject's circumstances. For example, effective doses may also varydepending upon means of administration, target site, physiological stateof the patient (including age, body weight and health), whether thepatient is human or an animal, other medications administered, orwhether treatment is prophylactic or therapeutic. Usually, the patientis a human but non-human mammals including transgenic mammals can alsobe treated. Treatment dosages are optimally titrated to optimize safetyand efficacy.

In certain embodiments, an in vitro assay is employed to help identifyoptimal dosage ranges. Effective doses may be extrapolated from doseresponse curves derived from in vitro or animal model test systems.

Generally, human antibodies have a longer half-life within the humanbody than antibodies from other species due to the immune response tothe foreign polypeptides. Thus, lower dosages of human antibodies andless frequent administration is often possible.

5.5.2 Detection & Diagnostic Uses

An anti-OX40 antibody described herein (see, e.g., Section 5.2) can beused to assay OX40 protein levels in a biological sample using classicalimmunohistological methods known to those of skill in the art, includingimmunoassays, such as the enzyme linked immunosorbent assay (ELISA),immunoprecipitation, or Western blotting. Suitable antibody assay labelsare known in the art and include enzyme labels, such as, glucoseoxidase; radioisotopes, such as iodine (¹²⁵I, ¹²¹I) carbon (¹⁴C), sulfur(³⁵S), tritium (³H), indium (¹²¹In) and technetium (⁹⁹Tc); luminescentlabels, such as luminol; and fluorescent labels, such as fluorescein andrhodamine, and biotin. Such labels can be used to label an antibodydescribed herein. Alternatively, a second antibody that recognizes ananti-OX40 antibody described herein can be labeled and used incombination with an anti-OX40 antibody to detect OX40 protein levels.

Assaying for the expression level of OX40 protein is intended to includequalitatively or quantitatively measuring or estimating the level of aOX40 protein in a first biological sample either directly (e.g., bydetermining or estimating absolute protein level) or relatively (e.g.,by comparing to the disease associated protein level in a secondbiological sample). OX40 polypeptide expression level in the firstbiological sample can be measured or estimated and compared to astandard OX40 protein level, the standard being taken from a secondbiological sample obtained from an individual not having the disorder orbeing determined by averaging levels from a population of individualsnot having the disorder. As will be appreciated in the art, once the“standard” OX40 polypeptide level is known, it can be used repeatedly asa standard for comparison.

As used herein, the term “biological sample” refers to any biologicalsample obtained from a subject, cell line, tissue, or other source ofcells potentially expressing OX40. Methods for obtaining tissue biopsiesand body fluids from animals (e.g., humans) are well known in the art.Biological samples include peripheral mononuclear blood cells.

An anti-OX40 antibody described herein can be used for prognostic,diagnostic, monitoring and screening applications, including in vitroand in vivo applications well known and standard to the skilled artisanand based on the present description. Prognostic, diagnostic, monitoringand screening assays and kits for in vitro assessment and evaluation ofimmune system status and/or immune response may be utilized to predict,diagnose and monitor to evaluate patient samples including those knownto have or suspected of having an immune system-dysfunction or withregard to an anticipated or desired immune system response, antigenresponse or vaccine response. The assessment and evaluation of immunesystem status and/or immune response is also useful in determining thesuitability of a patient for a clinical trial of a drug or for theadministration of a particular chemotherapeutic agent or an antibody,including combinations thereof, versus a different agent or antibody.This type of prognostic and diagnostic monitoring and assessment isalready in practice utilizing antibodies against the HER2 protein inbreast cancer (HercepTest™, Dako) where the assay is also used toevaluate patients for antibody therapy using Herceptin®. In vivoapplications include directed cell therapy and immune system modulationand radio imaging of immune responses.

In one embodiment, an anti-OX40 antibody can be used inimmunohistochemistry of biopsy samples.

In another embodiment, an anti-OX40 antibody can be used to detectlevels of OX40, or levels of cells which contain OX40 on their membranesurface, which levels can then be linked to certain disease symptoms.Anti-OX40 antibodies described herein may carry a detectable orfunctional label. When fluorescence labels are used, currently availablemicroscopy and fluorescence-activated cell sorter analysis (FACS) orcombination of both methods procedures known in the art may be utilizedto identify and to quantitate the specific binding members. Anti-OX40antibodies described herein can carry a fluorescence label. Exemplaryfluorescence labels include, for example, reactive and conjugatedprobes, e.g., Aminocoumarin, Fluorescein and Texas red, Alexa Fluordyes, Cy dyes and DyLight dyes. An anti-OX40 antibody can carry aradioactive label, such as the isotopes ³H, ¹⁴C, ³²P, ³⁵S, ³⁶Cl, ⁵¹Cr,⁵⁷Co, ⁵⁸Co, ⁵⁹Fe, ⁶⁷Cu, ⁹⁰Y, ⁹⁹Tc, ¹¹¹In, ¹¹⁷Lu, ¹²¹I, ¹²⁴I, ¹²⁵I, ¹³¹I,¹⁹⁸Au, ²¹¹At, ²¹³Bi, ²²⁵Ac and ¹⁸⁶Re. When radioactive labels are used,currently available counting procedures known in the art may be utilizedto identify and quantitate the specific binding of anti-OX40 antibody toOX40 (e.g., human OX40). In the instance where the label is an enzyme,detection may be accomplished by any of the presently utilizedcolorimetric, spectrophotometric, fluorospectrophotometric, amperometricor gasometric techniques as known in the art. This can be achieved bycontacting a sample or a control sample with an anti-OX40 antibody underconditions that allow for the formation of a complex between theantibody and OX40. Any complexes formed between the antibody and OX40are detected and compared in the sample and the control. In light of thespecific binding of the antibodies described herein for OX40, theantibodies thereof can be used to specifically detect OX40 expression onthe surface of cells. The antibodies described herein can also be usedto purify OX40 via immunoaffinity purification.

Also included herein is an assay system which may be prepared in theform of a test kit for the quantitative analysis of the extent of thepresence of, for instance, OX40 or OX40/OX40L complexes. The system ortest kit may comprise a labeled component, e.g., a labeled antibody, andone or more additional immunochemical reagents. See, e.g., Section 5.6below for more on kits.

In some aspects, methods for in vitro detecting OX40 in a sample,comprising contacting said sample with an antibody, are provided herein.In some aspects, provided herein is the use of an antibody providedherein, for in vitro detecting OX40 in a sample. In one aspect, providedherein is an antibody or pharmaceutical composition provided herein foruse in the detection of OX40 in a subject. In one aspect, providedherein is an antibody or pharmaceutical composition provided herein foruse as a diagnostic. In one preferred embodiment, the antibody comprisesa detectable label. In one preferred embodiment, OX40 is human OX40. Inone preferred embodiment, the subject is a human.

5.6 Kits

Provided herein are kits comprising one or more antibodies describedherein or conjugates thereof. In a specific embodiment, provided hereinis a pharmaceutical pack or kit comprising one or more containers filledwith one or more of the ingredients of the pharmaceutical compositionsdescribed herein, such as one or more antibodies provided herein. Insome embodiments, the kits contain a pharmaceutical compositiondescribed herein and any prophylactic or therapeutic agent, such asthose described herein. In certain embodiments, the kits may contain a Tcell mitogen, such as, e.g., phytohaemagglutinin (PHA) and/or phorbolmyristate acetate (PMA), or a TCR complex stimulating antibody, such asan anti-CD3 antibody and anti-CD28 antibody. Optionally associated withsuch container(s) can be a notice in the form prescribed by agovernmental agency regulating the manufacture, use or sale ofpharmaceuticals or biological products, which notice reflects approvalby the agency of manufacture, use or sale for human administration.

Also provided herein are kits that can be used in the above methods. Inone embodiment, a kit comprises an antibody described herein, preferablya purified antibody, in one or more containers. In a specificembodiment, kits described herein contain a substantially isolated OX40antigen (e.g., human OX40) that can be used as a control. In anotherspecific embodiment, the kits described herein further comprise acontrol antibody which does not react with a OX40 antigen. In anotherspecific embodiment, kits described herein contain one or more elementsfor detecting the binding of an antibody to a OX40 antigen (e.g., theantibody can be conjugated to a detectable substrate such as afluorescent compound, an enzymatic substrate, a radioactive compound ora luminescent compound, or a second antibody which recognizes the firstantibody can be conjugated to a detectable substrate). In specificembodiments, a kit provided herein can include a recombinantly producedor chemically synthesized OX40 antigen. The OX40 antigen provided in thekit can also be attached to a solid support. In a more specificembodiment, the detecting means of the above described kit includes asolid support to which a OX40 antigen is attached. Such a kit can alsoinclude a non-attached reporter-labeled anti-human antibody oranti-mouse/rat antibody. In this embodiment, binding of the antibody tothe OX40 antigen can be detected by binding of the said reporter-labeledantibody. Also, a kit or kit-of-parts comprising (a) an antibody orpharmaceutical composition of the present invention, and (b) acheckpoint targeting agent, an IDO inhibitor and/or a vaccine, isprovided.

The following examples are offered by way of illustration and not by wayof limitation.

6. EXAMPLES

The examples in this Section (i.e., Section 6) are offered by way ofillustration, and not by way of limitation.

6.1 Example 1: Generation of Novel Antibodies Against Human OX40

This example describes the generation and characterization of antibodiesthat bind to human OX40. In particular, this example describes thegeneration of human antibodies that specifically bind to human OX40 andexhibit a co-stimulatory effect on T cells.

6.1.1 Library Generation

The generation of the Retrocyte Display™ library is described herein.For the generation of library inserts, the total RNA was extracted viaphenol/chloroform from FACS sorted CD19 positive human B lymphocytesoriginated from two cord blood samples. The total RNA of each cord bloodsample (1 μg) was used for first-strand cDNA synthesis using RevertAidFirst Strand cDNA Synthesis Kit from Fermentas (Cat. No. K1621 andK1622). Antibody variable regions were amplified from the cDNA by PCRand cloned into retroviral expression vectors (pCMA). These constructswere subsequently used to transduce preB cells to express antibodies onthe surface using Retrocyte Display™ technology. The retroviralexpression vector contained 5′ and 3′ LTRs, immunoglobulin constantregion (IGHG1 or IGKC) comprising membrane anchor fraction (IGHG1) and aCD4 surface maker gene.

The light chain variable regions (VLs) were amplified by semi-nested PCRusing Vκ family-specific forward primers and a mixture of reverseprimers. The forward primers introduced the HindIII cloning site and thereverse primers introduced the Eco47III cloning site.

The heavy chain variable regions (VHs) were amplified by PCR using VHfamily-specific forward primers and a mixture of reverse primers. Theforward primers introduced the HindIII cloning site and the reverseprimers introduced the Eco47III cloning site.

The amplified VH and Vκ regions were digested at 37° C. overnight. Afterdigestion a band of the size of 400-450 bp was obtained and gel-purified(Macherey&Nagel, NucleoSpin Gel and PCR clean-up).

For the cloning of the heavy chain variable regions, construct 3181(pCMA-InsX Cg(iso3) loxP2-I-tr_huCD4-loxP) was digested withHindIII/Eco47III at 37° C. for 4 hours and a band of the size of 8362 bpwas gel-purified. For the cloning of the κ light chain variable regions,construct 3204 (pCMA-InsX Ck-I-CD4) was digested with HindIII/Eco47IIIat 37° C. for 4 hours and a band of the size of 7465 bp wasgel-purified.

The digested and purified antibody variable regions were ligated inframe into the appropriate expression vectors using a 1:3 vector toinsert ratio. Each VH and Vκ family was separately ligated intoretroviral expression vectors and concentrated 10-fold by precipitation.The precipitated VH and Vκ ligation reactions were also separatelytransformed into E. coli DH10B cells for library generation. Theseparate ligation, precipitation and transformation of each VH and Vκfamily allow the library to mirror the natural distribution offunctional germline genes, ensuring that the VH or Vκ families with ahigh number of functional germline genes are highly represented in thefinal library compared with families with a lower number of functionalgermline genes. After the transformation, E. coli cells were harvestedand combined to the final library. The quality of each library wascontrolled via diagnostic restriction digestion and analysis ofsequencing data. The library diversity was calculated from the data ofthe sequence analysis.

6.1.2 Recovery of Heavy and Light Chains from Pre-Selected preB CellClones

The library material generated as described above was used to identifyantibodies with a high binding affinity to OX40. The B cell clones werelysed and heavy and light chain variable regions were amplified from theinserted retroviral vector stably integrated in the genomic DNA usingPCR methods standard in the art. The amplified heavy and light chainvariable regions were subsequently cloned into mammalian expressionvectors containing the human heavy chain and light chain constantregions. The DNA plasmid preparations were subsequently used totransfect CHO cells and the expressed antibodies were tested usingsuspension array technology. Antibody heavy and light chains weresequenced at Microsynth (Balgach, Switzerland).

6.1.3 Biophysical Characterization of Anti-OX40 Antibodies

An antibody designated pab1949 was selected and characterized in anumber of assays as described below. The anti-OX40 antibody pab1949comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:60 and a light chain comprising the amino acid sequence of SEQ ID NO:50. The antibody pab1949 is a human IgG₁ antibody containing a T109Ssubstitution in the light chain constant domain (i.e., substitution ofthreonine with serine at position 109 relative to the wild type lightchain constant domain), numbered according to Kabat, which facilitatesthe cloning of the variable region in frame to the constant region. Thismutation is a conservative modification that does not affect antibodybinding or function. The wild type counterpart, named pab1949-1, whichcontains a threonine at position 109, numbered according to Kabat, wasalso generated. The antibody pab1949-1 is a human IgG₁ antibodycomprising a heavy chain of SEQ ID NO: 60 and a light chain of SEQ IDNO: 20.

6.1.3.1 Affinity Measurement by Bio-Layer Interferometry

The affinity of pab1949-1 was determined by Bio-layer Interferometry(BLI). Briefly, recombinant human OX40 antigen (OX40-Fc, R&D) wasdiluted using 1×PBS to obtain 1,000 μl of 0.2 μM and added to a 96-wellplate. pab1949-1 was diluted in 1×PBS to a concentration of 50 nM.Six-point serial dilutions of pab1949-1 were prepared from the 50 nMsolution using 1×PBS to obtain antibody dilutions ranging from 50 nM to0.78 nM and 100 μl of the respective antibody serial dilutions wereadded per well to a 96-well plate. Sensors were coated with the humanOX40 antigen using the 16-channel mode of Octet® at 25° C. for 5 minwith a threshold of 1.0 nm according to the manufacturer's instructions.For blocking, 0.5 mg/ml of a non-specific IgG₁ antibody was incubatedfor 10 minutes. The plate containing the serial antibody dilutions ofpab1949-1 was placed on the Octet® instrument. The assays were conductedaccording to the manufacturer's instructions. Binding and dissociationof pab1949-1 to the OX40 antigen were recorded for 3 minutes and 10minutes, respectively. Data were analyzed using the Octet® Data Analysissoftware and the result is shown in Table 5.

TABLE 5 Affinity measurement of pab1949-1 K_(a) (1/Ms) K_(d) (1/s) K_(D)(nM) 1.09 × 10⁶ 1.26 × 10⁻⁴ 0.116.1.3.2 Antibody Binding to Activated Human or Cynomolgus T Cells

The binding characteristics of the anti-OX40 antibodies pab1949 andpab1949-1 to human or cynomolgus OX40 were analyzed by flow cytometry.

Human PBMCs isolated via Ficoll gradient from healthy donor buffy coats(Research Blood Components, LLC) were enriched for untouched CD4+ andCD8+ T cells using magnetic-based separation (Miltenyi Biotec). Theenriched populations of T lymphocytes were then activated with CD3-CD28expansion beads (Miltenyi Biotec) with 500 U rIL-2 (R&D Systems) for 3days under recommended culture conditions, and 50 U rIL-2 thereafter.The recommended culture conditions were defined as cells cultured inRPMI-1640 media, supplemented with 10% fetal bovine serum, 10 mM HEPESand 1× Pen/Strep-Glutamine at 37° C. and 5% CO₂. Following activation,the cells were incubated with a surface antibody cocktail containing theconjugated antibodies of CD3 (BV711, OKT3), CD4 (BV605, OKT4), CD8a(BV650, RPA-T8), and pre-conjugated anti-OX40 antibodies or isotypecontrol (both Afluor488, 10 μg/ml) diluted in FACS buffer (PBS with 2%FBS) for 30 minutes at 4° C. Additional samples were set aside forsingle-stain compensation controls (CD45-BV650, CD45-Afluor488,CD45-BV605, and CD45-BV711). The cells were then washed with FACS buffertwice and analyzed using the LSRFortessa flow cytometer (BDBiosciences). The flow cytometry plots were analyzed using a combinationof FACS DIVA and WEHI Weasel software. The anti-OX40 antibody pab1949bound to activated human CD4+ T cells and CD8+ T cells (FIG. 1A).

A series of concentrations of pab1949-1 was tested for binding toactivated T cells to characterize a dose-response relationship. Inbrief, human peripheral blood mononuclear cells (PBMCs) were thawed andwashed with PBS. Negative isolation of T cells was performed withmagnetic beads (Miltenyi Biotec) and the purified T cells wereresuspended in RPMI+10% FBS and stimulated with anti-CD3/anti-CD28 beadsfor 72 hours at 37° C. and 5% CO₂. The cells were washed and blockedwith Fc blocking solution (Trustain, Biolegend) for 15 minutes at roomtemperature. The cells were washed again and stained with a serialdilution of pab1949-1 (10 to 0.00003 μg/ml) for 45 minutes at 4° C. inthe dark. The cells were washed and then stained with lineage markerantibodies including anti-CD3 fluorescein isothiocyanate (FITC) (cloneSP34) and anti-CD4 Brilliant Violet (BV) 510 (clone OKT4), together witha secondary antibody to detect pab1949-1 (anti-kappa IgG PE). Cells werewashed, fixed with 1.6% paraformaldehyde, and acquired using a BectonDickinson Fortessa flow cytometer. pab1949-1 demonstrated binding onlyto stimulated T cells, but not non-stimulated T cells (FIG. 1B). Thebinding of pab1949-1 to activated human CD4+ T cells was dose dependent(FIG. 1C).

Next, a number of quiescent immune cell subtypes were tested for bindingof pab1949-1. Human PBMCs were thawed and washed with PBS. To stain deadcells, infra-red (IR) viability dye was added and incubated for 15minutes at room temperature protected from light. Cells were washed andstained with an amine dye infra red (Life Technologies) for 15 minutesat room temperature. The cells were washed and Fc-blocked (Trustain FcX,Biolegend) for 10 minutes at room temperature. After washing, the cellswere incubated with 1 μg/ml of pab1949-1 or an IgG₁ isotype control for30 minutes at 4° C. protected from light. Cells were washed and stainedwith a secondary reagent (anti-Fc F(ab′) PE, Jackson Immune ResearchLaboratories) followed by lineage marker antibody staining thatincluded: anti-CD3 Phycoerithrin Cyanine 7 (PECy7, clone SP34.2),anti-CD8 BV510 (clone SK1), anti-CD4 Peridinin-Chlorophyll-ProteinComplex (PerCP) Cy5 (clone Ly200), and anti-CD14 FITC (clone TUK4).Cells were washed, fixed with 1.6% paraformaldehyde and acquired using aBecton Dickinson Fortessa flow cytometer. As shown in FIG. 1D, theanti-OX40 antibody pab1949-1 did not show detectable binding to CD14+cells, CD4+ T cells, CD8+ T cells, CD20+ B cells, or CD3-CD20-cells.

To test for species cross-reactivity, a cell binding assay was performedusing activated cynomolgus monkey (Macaca fascicularis) PBMCs. Briefly,viable cynomolgus monkey PBMCs (Worldwide Primates Inc.) were activatedwith Concanavalin-A (Sigma Aldrich, 5 μg/ml) and recombinant IL-2(Miltenyi, 20 U/ml) for 3 days in RPMI media supplemented with 10%heat-inactivated FBS at 37° C. in a 5% CO₂ humidified chamber. Followingactivation, the cells were incubated with human Fc-receptor block(Biolegend) for 15 minutes at room temperature to reduce nonspecificbinding. The anti-OX40 antibody pab1949 or a human IgG₁ isotype control(10 μg/ml) was added to the samples and incubated for 30 minutes at 4°C. Following one wash with the FACS buffer, an antibody cocktail,containing an APC-conjugated anti-human kappa antibody as well asantibodies specific for CD4 (BV605, OKT4) and CD8a (PE, RPA-T8), all at2.5 μg/ml, was diluted in the FACS buffer (PBS, 2 mM EDTA, 0.5% BSA andpH 7.2), added to each sample and incubated for 30 minutes at 4° C.Prior to staining, additional samples were set aside for single staincompensation controls (cyno-reactive: CD4-BV605, CD4-PE, and CD4-APC).The samples were washed twice in the FACS buffer and analyzed using theLSRFortessa flow cytometer (BD Biosciences). As shown in FIG. 1E,pab1949 bound to activated cynomolgus monkey CD4+ T cells.

6.1.3.3 OX40 Antibody Selectivity Assay

The selectivity of pab1949-1 for OX40 was assessed against other membersof the TNFR superfamily using suspension array technology as a multiplexassay. A number of TNFR family members were chemically coupled toLuminex® microspheres using standard NETS-ester chemistry. Purifiedmaterial of pab1949-1 was diluted in assay buffer (Roche 11112589001) to10 ng/ml, 100 ng/ml and 1000 ng/ml. Briefly, 25 μl of each dilution wasincubated in the dark (20° C., 650 rpm) with 1500 Luminex® microspheresin 5 μl assay buffer for 1 hour in 96 half-well filter plates(Millipore, MABVN1250). Luminex® microspheres (Luminex Corp, LC10001-01,LC10005-01, LC10010-01, LC10014-01, LC10015-01, LC10018-01, LC10022-01,LC10026-01, LC10052-01, LC10053-01 and LC10055-01) were coupled withrecombinant human LTBR-Fc (Acros Biosystems, LTR-H5251), anti-human IgG(F(ab)₂-specific, JIR, 105-006-097), recombinant human OX40-Fc (R&Dsystems, 3388-OX), recombinant human GITR-Fc (R&D, 689-GR), recombinanthuman DR6-Fc (SinoBiological, 10175-H02H), recombinant human DR3-Fc(R&D, 943-D3), recombinant human GITR-His (SinoBiological, 13643-H08H),recombinant human TWEAK R-Fc (SinoBiological, 10431-H01H), recombinanthuman OX40-His (SinoBiological, 10481-H08H), recombinant human 4-1BB-His(SinoBiological, 10041-H08H) or recombinant human BAFFR-Fc (R&D,1162-BR) via amine coupling with COOH bead surface. Standard curves weregenerated using duplicates of 25 μl of a human IgG₁ standard (Sigma,15154) with 1:3 dilution series (0.08-540 ng/ml). Detection was carriedout using 60 μl of goat anti-human IgG F(ab)₂ labeled with R-PE (2.5μg/ml; JIR 109-116-098, AbDSerotec Rapid RPE Antibody Conjugation Kit,LNK022RPE) and another hour of incubation time (20° C., 650 rpm). Plateswere analyzed using a Luminex® 200 system (Millipore). A total of 100beads were counted per well in a 48 μl sample volume. PE MFI values wereused to determine specific or nonspecific binding to the recombinantproteins mentioned above.

The antibody pab1949-1 showed specific binding to human OX40, and nosignificant binding to other TNFR family members was observed at testedconcentrations (data not shown).

6.2 Example 2: Functional Characterization of Anti-OX40 Antibodies

This example demonstrates the ability of the anti-OX40 antibodiespab1949 and pab1949-1 generated by the methods described above tofunction as agonists of OX40. The antibodies pab1949 and pab1949-1 wereassayed to determine their ability to costimulate primary human CD4+ orCD8+ T cells. In addition, pab1949 and pab1949-1, which are human IgG₁antibodies, were converted to human IgG₄ antibodies, pab2044 andpab2044-1, respectively. The antibody pab2044 shares the same heavychain variable region and the same light chain as pab1949 but comprisesa human IgG₄ constant region. The antibody pab2044 comprises a heavychain sequence of SEQ ID NO: 61 and a light chain sequence of SEQ ID NO:50. Similar to pab1949, pab2044 contains the T109S single amino acidsubstitution, a conservative modification that does not impact antibodybinding or function, in the light chain constant region to facilitatecloning. The wild type counterpart, pab2044-1, contains a threonine atposition 109, numbered according to Kabat, and comprises a heavy chainsequence of SEQ ID NO: 61 and a light chain sequence of SEQ ID NO: 20.Similarly, pab1949 and pab1949-1 were also converted to human IgG₂antibodies, pab2193 and pab2193-1, respectively. The antibody pab2193comprises a heavy chain sequence of SEQ ID NO: 62 and a light chainsequence of SEQ ID NO: 50. The antibody pab2193-1 comprises a heavychain sequence of SEQ ID NO: 62 and a light chain sequence of SEQ ID NO:20. In some assays, the functional activities of pab1949, pab1949-1,pab2044, pab2044-1, pab2193, or pab2193-1 were examined.

In some of the assays, the agonistic activity of the anti-OX40antibodies of this invention was compared to that of the referenceantibodies pab1784 and pab2045. The antibody pab1784 was generated basedon the variable regions of the antibody 11D4 provided in U.S. Pat. No.7,960,515 (herein incorporated by reference). The heavy chain of pab1784comprises the amino acid sequence of the heavy chain variable region of11D4 (SEQ ID NO: 26) and a human IgG₁ constant region of SEQ ID NO: 65.The light chain of pab1784 comprises the amino acid sequence of thelight chain variable region of 11D4 (SEQ ID NO: 24) and a constantregion of SEQ ID NO: 25.

The antibody pab2045 was generated based on the variable regions of theantibody 20E5 provided in International Publication No. WO 13/038191(herein incorporated by reference). The heavy chain of pab2045 comprisesthe amino acid sequence of the heavy chain variable region of 20E5 (SEQID NO: 30) and a human IgG₁ constant region of SEQ ID NO: 65. The lightchain of pab2045 comprises the amino acid sequence of the light chainvariable region of 20E5 (SEQ ID NO: 28) and a constant region of SEQ IDNO: 41.

6.2.1 Effect of Anti-OX40 Antibodies on Anti-CD3 Stimulated CD4+ T CellProliferation

To examine the effect of pab1949 on T cell proliferation, human PBMCsisolated via Ficoll gradient from healthy donor buffy coats (ResearchBlood Components, LLC) were enriched for untouched CD4+ T cells usingmagnetic-based separation (Stemcell Technologies). Cellularproliferation was determined by monitoring dilution ofcarboxyfluorescein diacetate sucinimidyl ester (CFSE) dye within dividedcells (Quah B J et al., (2007) Nat Protoc, 2(9): 2049-56). The enrichedCD4+ T cells were labeled with 10 μM CellTrace™ CFSE (Life Technologies)for 7 minutes at 37° C. After extensive washes, the cells were suspendedin RPMI1640 media supplemented with 10% heat-inactivated FBS at 1×10⁶cells/ml. A total of 100 μl (1×10⁵ cells) was seeded into each well offlat bottom 96 well plates pre-coated with anti-CD3 antibody (3 μg/ml,BD Biosciences) together with either 5 μg/ml of pab1949, 5 μg/ml of IgG1isotype control, or 2 μg/ml of anti-CD28 antibody (BD Biosciences) andcultured at 37° C. and 5% CO₂. On day 5, the cells were stained with 0.5μI/well of PerCP-Cy5.5 labeled anti-CD4 antibody in FACS buffer (2% FBSin PBS) at 4° C. for 30 minutes and the percentage of CFSE low CD4+cells was determined by Flow Cytometry on a LSRFortessa (BDBiosciences). The flow cytometry data were analyzed using FlowJo.

The activity of pab2044 was assessed using a similar assay as describedabove where CD4+ T cells that were labeled with CFSE were seeded onto 96well plates pre-coated with anti-CD3 antibody (3 μg/ml, BD Biosciences)together with either 5 μg/ml of pab2044, 5 μg/ml of IgG₄ isotype control(pab2031), or 2 μg/ml of anti-CD28 antibody (BD Biosciences). Thepercentage of CFSE low CD4+ cells was examined by Flow Cytometry on day5.

FIGS. 2A and 2B are histograms from a representative flow cytometryanalysis of CD4+ T cell proliferation induced by costimulation withanti-OX40 antibodies, showing cell numbers (Y-axis) and the level offluorescence emitted (X-axis) by the CFSE labeled CD4+ T cells. EnhancedCD4+ T cell proliferation is shown by an increased percentage of cellswith a diminished level of fluorescence emitted by CFSE. The percentagesof CFSE low CD4+ cells were indicated in the histograms. Both pab1949(FIG. 2A) and pab2044 (FIG. 2B), when plate-bound, induced CD4+ T cellproliferation when added to cells activated with suboptimalconcentrations of anti-CD3 antibody.

Next, the dose response of pab1949 in inducing T cell proliferation wasmeasured. PBMCs isolated via Ficoll gradient from healthy donor buffycoats (Research Blood Components, LLC) were enriched for untouched CD4+T cells using magnetic-based separation (Stemcell Technologies). Theenriched population of CD4+ T cells was then labeled with 10 μMCellTrace™ CFSE (Life Technologies) for 7 min at 37° C. After extensivewashes, the cells were suspended in RPMI1640 media supplemented with 10%heat-inactivated FBS at 1×10⁶/ml. 100 μl (1×10⁵) of cells was seededinto each well of flat bottom 96 well plates pre-coated with anti-CD3antibody (3 μg/ml, BD Biosciences) together with varying concentrationsof pab1949 or an IgG₁ isotype control and cultured at 37° C. and 5% CO₂.On day 4, cells were stained with 0.5 μl/well of APC-labeled anti-CD4antibody in FACS buffer (2% FBS in PBS) at 4° C. for 30 minutes and thepercentage of CFSE low CD4+ cells was determined by Flow Cytometry on aLSRFortessa (BD Biosciences).

As shown in FIG. 2C, the anti-OX40 antibody pab1949 was able to maintaina high level of T cell proliferation at pharmacologically relevantantibody concentrations. CD4+ T cell proliferation was a substantiallyincreasing function of the concentrations of pab1949 between 0.2 μg/mland 20 μg/ml (FIG. 2C).

6.2.2 Effect of Anti-OX40 Antibodies on Anti-CD3 Stimulated Human PBMCCytokine Production

As further evidence for the agonistic activity of the anti-OX40antibodies pab1949 and pab1949-1, cytokine production under suboptimalanti-CD3 stimulation was measured.

For an intracellular cytokine staining experiment, human PBMCs isolatedvia Ficoll gradient from healthy donor buffy coats (Research BloodComponents, LLC) were stored in liquid nitrogen and thawed on the day ofthe experiment. The cells were resuspended in cell culture media(RPMI+10% FBS+20 U/mL of IL-2) and added to 96-well culture plates thatcontained plate-bound anti-CD3 antibody at various suboptimalconcentrations plus 5 μg/ml of the anti-OX40 antibody pab1949 or theisotype control IgG₁ antibody. The samples were incubated for 3 days at37° C. and 5% CO₂. After activation, to inhibit intracellular proteintransport, the cells were treated with Brefeldin A (BD Biosciences)according to the manufacturer's instructions and the samples wereincubated for 6 hours at 37° C. and 5% CO₂. After the incubation thecells were stained with a viability amine dye (Life technologies) fordead cells. After washing with the FACS buffer (PBS, 2% FBS, pH 7.2), anantibody cocktail containing antibodies specific for CD3 (APC Cy7,SP34.2), CD4 (PercP Cy5.5, L200), and CD8a (PE Cy7, SK1) diluted in coldFACS buffer was added to each sample and incubated for 10 minutes at 4°C. The cells were fixed and permeabilized with Cytofix-Cytoperm (BDBiosciences) for intracellular staining according to the manufacturer'sinstructions. The PBMCs were stained with antibodies specific for IFNγ(Alexa647, B27) and TNFα (PE, Mab 11) and incubated at room temperaturefor 10 minutes. Prior to staining, beads binding kappa light chains ofmouse IgG antibodies were stained with the antibodies used to stain thecells using single stained compensation controls. Samples were washedusing 1×Perm-wash buffer (BD Biosciences) and analyzed using the FACSCanto flow cytometer (BD Biosciences). The flow cytometry plots wereanalyzed using the Flojo software.

PBMCs from four different donors were tested: donor KM, donor TM, donorGS, and donor SB. For all the donors, pab1949 demonstrated costimulatoryactivity on human T cells, inducing IFNγ+ TNFα+ polyfunctional CD4+ Tcells and CD8+ T cells and TNFα+ monofunctional CD4+ T cells and CD8+ Tcells (FIGS. 3A, 3B, and 3C). In PBMCs from donor GS, pab1949 was alsoable to increase the percentage of IFNγ+ monofunctional T cells (FIG.3B).

Next, a dose titration of the anti-OX40 antibody pab1949-1 was tested ina suboptimal anti-CD3 stimulation assay similar to the one describedabove using cells derived from PBMCs of donor GS. Briefly, PBMCs wereincubated with plate-bound anti-CD3 antibody (0.8 μg/ml) and plate-boundpab1949-1 or an IgG₁ isotype control antibody (0, 0.3, 1, 3, 6, 12, 25,or 50 μg/ml) for 4 days at 37° C. and 5% CO₂. After activation, toinhibit intracellular protein transport, the cells were treated withBrefeldin A (BD Biosciences) according to the manufacturer'sinstructions and the samples were incubated for 6 hours at 37° C. and 5%CO₂. After the incubation, the cells were stained with a FITC viabilityamine dye (Life technologies) to differentiate live and dead cells.After washing with cold buffer (1×PBS+2% FBS, pH 7.2), an antibodycocktail containing anti-CD3 (APC Cy7, SP34.2), anti-CD4 (PercP Cy5.5,L200), and anti-CD8a (PE Cy7, SK1) was added to each sample andincubated for 10 minutes at 4° C. The cells were fixed and permeabilizedwith Cytofix-Cytoperm (BD Biosciences) for intracellular stainingaccording to the manufacturer's instructions. The PBMCs were stainedwith anti-IFNγ (Alexa647, B27) and anti-TNFα (PE, Mab 11) antibodies andincubated at room temperature for 10 minutes. Samples were washed using1×Perm-wash buffer (BD Biosciences) and acquired using a FACScanto flowcytometer (BD Biosciences). The flow cytometry plots were analyzed usingFlojo software. As shown in FIGS. 3D-3F, the anti-OX40 antibodypab1949-1 demonstrated co-stimulatory activity and increased thepercentage of TNFα+ CD4+ T cells, IFNγ+ TNFα+ polyfunctional CD8+ Tcells, and IFNγ+ CD8+ T cells in a dose-dependent manner.

The co-stimulatory activity of a ranging dose of pab1949-1 was furthertested using cells derived from PBMCs of additional donors in thesuboptimal anti-CD3 stimulation assay described above. The anti-OX40antibody pab1949-1 and an IgG₁ isotype control antibody were tested at0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml. The anti-OX40 antibodypab1949-1 consistently increased the percentage of IFNγ+ and/or TNFα+ Tcells in PBMCs from multiple donors (FIGS. 4A-4C).

Notably, for PBMCs from many donors, the percentage of IFNγ+ and/orTNFα+ T cells induced by the anti-OX40 antibody pab1949-1 was asubstantially increasing function of antibody concentration across awide range of antibody concentrations tested (FIGS. 3D-3F and 4A-4C).

To examine further the agonistic activity of the anti-OX40 antibodypab1949, the quantity of cytokines secreted was measured. Human PBMCsisolated via Ficoll gradient from healthy donor buffy coats (ResearchBlood Components, LLC) were stored in liquid nitrogen and thawed on theday of the experiment. The cells were resuspended in cell culture media(RPMI+10% FBS+20 U/mL of IL-2) and added to 96-well culture plates thatcontained plate-bound anti-CD3 antibody at various suboptimalconcentrations plus 5 μg/ml of the anti-OX40 antibody pab1949 or theisotype control IgG₁ antibody. The samples were incubated at 37° C. and5% CO₂ and cell culture supernatant was collected after either 4 days(SB #1A) or 3 days (SB #1B, SB #2, and GS). The samples were testedusing the V-PLEX Proinflammatory Panel1 (human) Kit (Meso ScaleDiscovery) for the production of IL-2, TNFα, IL-10, IL-4, and IL-13according to the manufacturer's instructions.

As depicted in FIG. 5A, the anti-OX40 antibody pab1949 costimulatedcytokine production in human PBMCs from two different donors: donor SBand donor GS. Cytokine production of PBMCs from donor SB was tested intwo separate experiments: SB #1A and SB #1B show results from a firstexperiment where cytokines were measured after 4 days and 3 days uponstimulation, respectively; and SB #2 shows results from a secondexperiment where cytokines were measured after 3 days upon stimulation.

Next, cytokine secretion induced by a dose titration of pab1949-1 wasexamined using cells derived from PBMCs of donor GS in a suboptimalanti-CD3 stimulation assay similar to the one described above. In brief,PBMCs were incubated with plate-bound anti-CD3 antibody (0.8 μg/ml) andplate-bound pab1949-1 or an IgG₁ isotype control antibody (0, 0.3, 1, 3,6, 12, 25, or 50 μg/ml) for 4 days at 37° C. and 5% CO₂. Afteractivation, cell culture supernatant was collected for detection ofcytokines using the Human TH1/TH2 10-Plex tissue culture kit (Meso ScaleDiscovery).

As shown in FIGS. 5B-5D, the anti-OX40 antibody pab1949-1 stimulatedTNFα, IL-10, and IL-13 production in a dose-dependent manner.

The co-stimulatory activity of pab1949-1 in inducing cytokine secretionwas further confirmed using cells derived from PBMCs of additionaldonors. Briefly, PBMCs were incubated with plate-bound anti-CD3 antibody(0.8 μg/ml) and plate-bound pab1949-1 or an IgG₁ isotype controlantibody (0, 0.7, 1.6, 3.1, 6.3, 12.5, 25, or 50 μg/ml) for 4 days at37° C. and 5% CO₂. After activation, the amount of cytokines secreted tothe supernatant was measured using the non-human primate (NHP) V-Plexassay kit (Meso Scale Discovery).

For all the donors tested, pab1949-1 dose-dependently increased thesecretin of GM-CSF (FIGS. 6A-6C), IL-2 (FIGS. 7A-7C), and TNFβ (FIGS.8A-8C).

For PBMCs from many donors, the secretion of cytokines (GM-CSF, IL-2,TNFα, TNFβ, IL-10, and IL-13) induced by the anti-OX40 antibodypab1949-1 was a substantially increasing function of antibodyconcentration across a wide range of antibody concentrations (FIGS.5B-5D, 6A-6C, 7A-7C, and 8A-8C).

6.2.3 Effect of Anti-OX40 Antibody in a T Effector Cell: T RegulatoryCell Co-Culture Assay

Next, the anti-OX40 antibody pab1949-1 was examined for its activity ina T effector cell (Teff): T regulatory cell (Treg) co-culture assay. Inbrief, human PBMCs isolated via Ficoll gradient from healthy donor buffycoats (Research Blood Components, LLC) were stored in liquid nitrogenand thawed on the day of the experiment. T regulatory cells and Teffector cells were isolated by magnetic bead separation(CD4⁺CD25⁺CD127^(dim/−) Regulatory T Cell Isolation Kit II and Pant Tcell kit, respectively, Miltenyi Biotec). T regulatory cells were thenactivated for 2 days by incubating with anti-CD3/anti-CD28/anti-CD2beads (Miltenyi Biotec) at a ratio of 1:2 (T cell:bead) in cell culturemedia (RPMI+10% FBS). After activation, T regulatory cells and Teffector cells were added to 96-well culture plates at a 1:3 (Treg:Teff)ratio in the presence of anti-CD3/anti-CD28/anti-CD2 beads, soluble orcrosslinked (using anti-Fc F(ab′)₂, Jackson ImmunoResearch) pab1949-1 oran IgG₁ isotype control (10 μg/ml). The samples were incubated for 4days at 37° C. and 5% CO₂. After activation, the supernatant wascollected and IL-10 or IL-2 was measured using AlphaLISA® (PerkinElmer).

In this in vitro Teff:Treg co-culture assay, the anti-OX40 antibodypab1949-1 relieved suppression of Teff cell populations by Treg cells,as evidenced by enhanced IL-2 production (FIG. 9A) and reduced IL-10production (FIG. 9B) from pab1949-1-treated cells as compared withisotype-treated cells.

6.2.4 Effect of Anti-OX40 Antibodies on Human PBMCs Upon StaphylococcusEnterotoxin A (SEA) Stimulation

The functional activity of the anti-OX40 antibodies pab1949 andpab1949-1 on primary human PBMCs was further assessed followingStaphylococcus Enterotoxin A (SEA) stimulation. Cryopreserved PBMCs (10⁵cells/well) in RPMI1640 supplemented with penicillin, streptomycin and10% FBS (Hyclone) were added to 96-well NUNCLON delta surface plates(NUNC™). The cells were cultured in the absence or presence of a fixedconcentration (10 μg/ml in FIGS. 10A and 10B) or varying concentrations(20, 4, 0.8, 0.16, 0.032, 0.0064, and 0.00128 μg/ml in FIGS. 10C and10D; 50, 10, 2, 0.4, 0.08, 0.016, and 0.0032 μg/ml in FIG. 10E) ofanti-OX40 antibody or isotype control and 100 ng/ml of SEA (ToxinTechnologies) for 5 days at 37° C., 5% CO₂ and 97% humidity. Clarifiedsupernatant was collected and stored at −80° C. until analysis. Thetiters of cytokines were generated using electrochemiluminescence (MesoScale Discovery) for IL-2 and IL-10.

The anti-OX40 antibody pab1949 showed agonistic activity in this primaryhuman PBMC assay, inducing IL-2 production (FIG. 10A) and suppressingIL-10 production (FIG. 10B). The enhancement of IL-2 production bypab1949 at 10 μg/ml was superior to that observed with the referenceanti-OX40 antibodies pab1784 and pab2045 (FIG. 10A). FIGS. 10C, 10D, and10E are dose-response curves from three independent experiments showingthe fold change of IL-2 following costimulation with differentconcentrations of pab1949, pab1949-1, or the reference antibodiespab1784 and pab2045. The antibodies pab1949 and pab1949-1 exhibited adifferent dose-response relationship from the reference antibodies andwere able to induce high levels of IL-2 production at pharmacologicallyrelevant antibody concentrations. IL-2 production induced by pab1949 orpab1949-1 was a substantially increasing function of antibodyconcentration across a wide range of antibody concentrations (e.g.,between 0.032 and 20 μg/ml, as shown in FIGS. 10C and 10D, or between0.0032 and 50 μg/ml, as shown in FIG. 10E).

Next, the functional activity of the IgG₁ antibody pab1949-1 and theIgG₂ antibody pab2193-1 was compared in the primary human PBMC assaydescribed above. Briefly, cryopreserved human PBMCs (Research BloodComponents) were plated at 10⁵ cells/well in RPMI1640 mediumsupplemented with Normocin™ (Invivogen, # ant-nr) and 10%heat-inactivated FBS (Gibco, Invitrogen Corporation) in 96-well NUNCLONdelta surface plates. Cells were incubated with increasingconcentrations (50, 10, 2, 0.4, 0.08, 0.016, and 0.0032 μg/ml) ofpab1949-1, pab2193-1, an IgG₁ isotype control antibody, or an IgG₂isotype control antibody, and 100 ng/ml SEA superantigen (ToxinTechnologies) for 5 days at 37° C., 5% CO₂, and 97% humidity. Clarifiedsupernatant was collected and stored at −80° C. until analysis.Concentrations of IL-2 were measured by ELISA.

As shown in FIG. 10F, both the IgG₁ antibody pab1949-1 and the IgG₂antibody pab2193-1 induced IL-2 production in human PBMCs. Similar topab1949-1, pab2193-1 also exhibited a dose-response relationship inwhich the IL-2 production was a substantially increasing function ofantibody concentration.

Further, the role of FcγR interaction in the functional activity of theanti-OX40 antibody pab1949-1 was examined by comparing the IgG₁ antibodypab1949-1 with an aglycosylated variant pab1949-1-N297A. pab1949-1-N297Ashares the heavy chain variable region and light chain sequences withpab1949-1 but comprises an N297A substitution in the heavy chainconstant region, numbered according to the EU numbering system.

Human PBMCs isolated via Ficoll gradient from healthy donor buffy coats(Research Blood Components, LLC) were stored in liquid nitrogen andthawed on the day of the experiment. The cells were resuspended in cellculture media (RPMI+10% heat-inactivated FBS) and incubated with 100ng/ml SEA (Toxin Technologies) and a dose titration of pab1949-1,pab1949-1-N297A, or an IgG₁ isotype control antibody (0-50 μg/ml) for 5days at 37° C. and 5% CO₂. The supernatant were collected and thentested for IL-2 using AlphaLISA® (Perkin Elmer).

As shown in FIG. 10G, both pab1949-1 and pab1949-1-N297A induced IL-2production in a dose-dependent manner in human PBMCs upon SEAstimulation. The presence of a key glycosylation at a single N-linkedglycosylation site at asparagine 297 (N297) is lost on thepab1949-1-N297A variant antibody leading to loss of binding of its Fcfragment to FcγRs. This variant antibody exhibited reduced agonisticactivity compared with the wild type counterpart.

6.2.5 Effect of Agonistic Anti-OX40 Antibody on OX40 NF-κB-LuciferaseReporter Cell Line

The ability of the anti-OX40 antibody pab1949-1 to mediate signaltransduction in T cells was measured using a human OX40 NF-κB-luciferasereporter cell line. The reporter cells generated using a Jurkat cellline were resuspended in assay media (RPMI+10%FBS+Penicillin/Streptomycin/Glutamate+1 μg/ml puromycin) and incubatedwith various concentrations of soluble pab1949-1 (0-6 μg/ml) or an IgG₁isotype control antibody in the presence of an anti-Fc reagent(complexed condition) or not (soluble condition). Plates were incubatedfor 2 hours at 37° C. and 5% CO₂. After incubation, the plates wereequilibrated at room temperature and then an equal volume of roomtemperature Nano-Glo reagent (Promega) was added. Luminescence was readusing an EnVision multilabel reader 2100.

Only crosslinked pab1949-1 induced significant activation of the OX40NF-κB-luciferase reporter cell line (FIG. 11B). Soluble pab1949-1induced minimal activation of the reporter cell line and the IgG₁isotype control antibody did not induce detectable levels of luciferaseexpression (FIGS. 11A and 11B).

6.2.6 Effect of Agonistic Anti-OX40 Antibody on Fc Gamma Receptor IIIAReporter Cell Line

In this example, the ability of the IgG₁ antibody pab1949-1 and the IgG₄antibody pab2044-1 to co-engage OX40 and signal via activating Fc gammareceptors was evaluated using a reporter cell line expressing Fc gammareceptor IIIA together with target cells expressing human OX40. JurkatNFAT-luciferase reporter cells overexpressing FcγRIIIA (158 V/Vpolymorphism) (Promega) were used as effector cells. Binding ofantibody/antigen complex, wherein the antigen is located on the surfaceof target cells, to FcγRIIIA on effector cells signals to thepromoter/reporter construct and results in luciferase gene expression.

OX40-overexpressing cells (PHA-activated Hut102 cells) were co-culturedwith the FcγRIIIA reporter cells in the presence of a dose titration ofsoluble pab1949-1, pab2044-1, an IgG₁ isotype control, or an IgG₂isotype control (0-10 μg/ml). Activation of the reporter cells wasassessed according to the manufacturer's instructions and the relativelight units (RLU) were recorded. Δ RLU was calculated as the RLU of theanti-OX40 antibody minus that of the isotype control. As shown in FIG.12A, when bound to OX40-expressing cells, only the IgG₁ antibodypab1949-1 activated the FcγRIIIA reporter cells.

6.2.7 Effect of Agonistic Anti-OX40 Antibody on Fc Gamma Receptor IIAReporter Cell Line

Next, the ability of the IgG₁ antibodies pab1949-1 andpab1949-1-S267E/L328F as well as the IgG₂ antibody pab2193-1 toco-engage OX40 and signal via FcγRIIA was evaluated using a reportercell line expressing FcγRIIA (Promega) together with target cells(Jurkat cells expressing human OX40). pab1949-1-S267E/L328F shares theheavy chain and light chain sequences with pab1949-1 but comprises S267Eand L328F substitutions in the heavy chain constant region, numberedaccording to the EU numbering system.

Jurkat cells expressing FcγRIIA with the high affinity 131 H/Hpolymorphism and an NFAT response element driving expression of fireflyluciferase were used as effector cells. Briefly, 25 μl of target cells(6×10⁶ cells/ml) were mixed with 25 μl of serially diluted antibodies induplicate wells of 96-well white assay plates. The antibodies testedwere pab1949-1, pab1949-1-S267E/L328F, pab2193-1, an IgG₁ isotypecontrol antibody, and an IgG₂ isotype control antibody. Then, 25 μl ofeffector cells (6×10⁶ cells/ml) were added to each well, resulting in a1:1 effector to target ratio. The plates were incubated for 20 hours at37° C. and 5% CO₂. After this incubation, Bio-Glo Luciferase AssayReagent (Promega) was thawed at room temperature and 75 μl was added toeach well. Within 5-10 minutes, luminescence was measured using theEnVision multilabel plate reader (PerkinElmer). Background luminescencewas subtracted from each sample reading and the adjusted relative lightunits (RLU) were recorded.

As shown in FIG. 12B, when bound to cells expressing OX40, the IgG₂antibody pab2193-1 showed strongest activation of FcγRIIA^(H131),followed by pab1949-1-S267E/L328F and pab1949-1.

6.2.8 Interaction of Anti-OX40 Antibody with T Regulatory Cells or TEffector Cells

In this example, expression of human OX40 by activated natural Tregulatory cells (nTreg) and T effector (Teff) cells was examined. PBMCsisolated from healthy donors were enriched for untouched CD3+ T cells(Teff) or CD4+ CD25+ CD45RA+ T cells (nTregs) using magnetic-basedseparation. T lymphocytes were activated with anti-CD3/CD28 coupledbeads with 500 U rIL-2 for 4 days, and 50 U rIL-2 for an additional 4days. Following 8 days of activation, T cells were harvested and stainedwith the live/dead fixable Near-IR dead cell stain in PBS for 20 minutesat 4° C. A surface antibody cocktail, containing the conjugatedantibodies against CD4 (BV605, OKT4), CD8a (BV650, RPA-T8), CD127(BV421, A01905), CD25 (APC, M-A251), and OX-40 (PE, ACT35) diluted inbuffer (PBS with 2% FBS), was added to each sample and incubated for 30minutes at 4° C. Cells were then washed with buffer and fixed andstained with an intracellular antibody cocktail, containing theconjugated antibodies against CD3 (BV711, OKT3) and Foxp3 (AF488,PCH101) diluted in buffer. One sample from each T cell population wasalso stained with fluorescence minus one (FMO) controls for OX40 usingmouse anti-human IgG1-PE isotype control. Samples were analyzed by flowcytometry. PE-conjugated Quantibrite beads were run simultaneously andused to quantitate OX40 receptor density, as per manufacturer'sinstructions.

As shown in FIG. 13A, the surface expression of human OX40 on activatednTreg cells was higher than that on activated CD4+ or CD8+ T effectorcells.

In a similar study, activated nTregs and Teffs from two donors werestained with a commercial anti-OX40 antibody (BER-ACT35 clone) or anisotype control antibody and analyzed by flow cytometry. Delta meanfluorescence intensity (Δ MFI) represents the MFI of the anti-OX40antibody minus that of the isotype control. The results are shown inFIG. 13B.

Next, the ability of the anti-OX40 antibody pab1949 to co-engage OX40and signal via activating Fc gamma receptors was evaluated using thereporter cell line expressing Fc gamma receptor IIIA (FcγRIIIA)described above together with activated T effector (Teff) or nTregcells, generated as described. The anti-OX40 antibody pab1949 or an IgG₁isotype control was serially diluted with 3-fold dilutions with astarting final concentration of 10 μg/ml. In duplicate wells, 25 μl ofeach antibody dilution was added to the Teff or nTreg cells. JurkatNFAT-luciferase reporter cells overexpressing FcγRIIIA (158 V/Vpolymorphism) were added in a 1:1 effector to target ratio. Plates wereincubated for 20 hours and then analyzed using a Bio-Glo LuciferaseAssay Reagent (Promega). Background luminescence (blank outer wells) wassubtracted from each sample reading and the adjusted relative lightunits (RLU) were recorded. Δ RLU is shown in FIG. 13C, representing theRLU of the anti-OX40 antibody minus that of the isotype control.

The study depicted in FIG. 13C was repeated using a slightly modifiedprotocol. In brief, buffy coats from a healthy volunteer (Research BloodComponents) were used for isolation of primary T regulatory cells and Teffector cells. Both T cell subsets were purified by magnetic beadseparation (CD4⁺CD25⁺CD127^(dim/−) Regulatory T Cell Isolation Kit IIand Pant T cell kit, respectively, Miltenyi Biotec) and then activatedfor 7 days by incubating the cells with anti-CD3/anti-CD28/anti-CD2beads (Miltenyi Biotech) at a ratio of 1:4 (T cell:bead) in cell culturemedia (RPMI+10% FBS). Activated Treg cells or Teff cells wereco-cultured with the FcγRIIIA-expressing Jurkat NFAT-luciferase reportercells (Promega) described above in the presence of a dose titration ofsoluble pab1949-1 or an IgG₁ isotype control antibody (0-10 μg/ml).Activation of the reporter cells was assessed according to themanufacturer's instructions and Δ RLU is shown in FIG. 13D.

Consistent with the differential surface OX40 expression betweenactivated nTregs and activated CD4+ or CD8+ T effector cells (FIGS. 13Aand 13B), the anti-OX40 antibodies pab1949 (FIG. 13C) and pab1949-1(FIG. 13D) preferentially labeled activated nTreg cells, inducingFcγRIIIA-dependent signaling in the reporter cell line.

To evaluate if OX40 overexpression was a feature of regulatory T cellslocated within tumor microenvironment, OX40 expression was compared on Tcells isolated from the blood of healthy human donors (FIG. 14A, a-c,n=3) or from tumor tissues of non-small cell lung cancer (NSCLC)patients (FIG. 14A, d-f, n=3). To eliminate background binding ofantibodies to immune populations, all the cells were incubated withpurified CD16/32 antibody (10 μg/ml, 20 minutes at room temperature)prior to the addition of cell-surface and intracellular antibodies.Following FcR-blockade, all the samples were incubated withAPC-conjugated anti-OX40 antibody (clone Ber-ACT35) or isotype controland a cell-surface antibody lineage-cocktail (CD3-FITC, CD25-PECy7,CD4-BV650 and CD8a-PE) for 45 minutes on ice (1 μg/ml each), washedthree times with FACS buffer (PBS, EDTA and 0.5% BSA), followed byfixation/permeabilization and incubation with Pacific Blue-conjugatedFOXP3 (fix/perm and incubation each 45 minutes on ice, 1 μg/ml). Thestained samples were then analyzed using an LSRFortessa flow cytometer(BD Biosciences). The cell populations in FIG. 14A were defined as:Tconv (CD3+, CD4+, CD8a−, CD25low, FOXP3−) or Treg (CD3+, CD4+, CD8a−,CD25high, FOXP3+).

As shown in FIG. 14A, OX40 surface expression was highest on regulatoryT cells isolated from the tumor tissues of NSCLC patients, with littleor no detectable level on Treg or conventional T cells from healthydonors.

Similar analyses were carried out for other tumor types. In brief,frozen dissociated tumor samples (Conversant) or PBMCs were thawed inAutoMACS Rinsing Solution (washing buffer, Miltenyi Biotec) and cellswere Fc-blocked (Trustain FcX, Biolegend) before cell surface staining.Cells were washed with washing buffer and stained for 45 minutes at 4°C. with lineage marker antibodies that included: anti-CD3 (clone SP34),anti-CD4 (clone OKT4), anti-CD8 (clone SK1), anti-CD25 (clone MA-251),and anti-OX40 (clone BER-ACT35). Cells were washed and permeabilizedwith forkhead box P3 (FOXP3)/Transcription Factor Staining Buffer Set(eBioscience) according to the manufacturer's instructions. Afterpermeabilization, the cells were stained with anti-FOXP3 eFluor450(clone PCH101, eBioscience). Stained samples were acquired using a BDBiosciences Fortessa flow cytometer and data were analyzed using Flojosoftware.

Samples from multiple tumor types, including ovarian cancer, colorectalcarcinoma (CRC), endometrial carcinoma, renal cell carcinoma (RCC),non-small cell carcinoma (NSCLC), and breast cancer, demonstrated higherOX40 expression in tumor-associated T regulatory cells than intumor-associated T effector cells (FIGS. 14B, 14C, and 14D).

6.2.9 Effect of Anti-OX40 Antibody on Anti-CD3 Stimulated CynomolgusPBMC Cytokine Production

Next, the agonistic activity of the anti-OX40 antibody pab1949-1 oncynomolgus PBMCs was examined using a suboptimal anti-CD3 stimulationassay. Briefly, frozen cynomolgus PBMCs (World Wide Primates) werestored in liquid nitrogen and thawed on the day of the experiment. Thecells were resuspended in cell culture media (RPMI+10% FBS+20 U/ml ofIL-2) and incubated with plate-bound anti-CD3 antibody (0.8 μg/ml) andplate-bound pab1949-1 or an IgG₁ isotype control antibody (0, 0.8, 1.6,3.1, 6.3, 12.5, 25, or 50 μg/ml) for 4 days at 37° C. and 5% CO₂. Cellculture supernatant was collected and secreted cytokines were examinedusing the non-human primate (NHP) V-Plex assay kit (Meso ScaleDiscovery).

The anti-OX40 antibody pab1949-1 dose-dependently enhanced theproduction of GM-CSF (FIGS. 15A and 15B), IL-17 (FIGS. 16A and 16B),TNFβ (FIGS. 17A and 17B), IL-5 (FIGS. 18A and 18B), and IL-10 (FIGS. 19Aand 19B) in PBMCs of multiple cynomolguses.

6.2.10 Effect of Anti-OX40 Antibody on Cynomolgus PBMCs UponStaphylococcus Enterotoxin A (SEA) Stimulation

The ability of pab1949-1 to co-stimulate cynomolgus PBMCs was furtheranalyzed following Staphylococcus Enterotoxin A (SEA) stimulation.Frozen cynomolgus PBMCs (World Wide Primates) were stored in liquidnitrogen and thawed on the day of the experiment. The cells wereresuspended in cell culture media (RPMI+10% heat-inactivated FBS) andincubated with the SEA antigen (100 ng/ml) as well as a dose titrationof pab1949-1 or an IgG₁ isotype control antibody 0, 0.8, 1.6, 3.1, 6.3,12.5, 25, or 50 μg/ml) for 5 days at 37° C. and 5% CO₂. Afteractivation, the cell culture supernatant was collected and secretedcytokines were examined using the non-human primate (NHP) V-Plex assaykit (Meso Scale Discovery).

As shown in FIGS. 20A and 20B, the anti-OX40 antibody pab1949-1increased IL-2 production in cynomolgus PBMCs from two donors.

6.3 Example 3: Epitope Mapping of Anti-OX40 Antibodies

In this example, the epitopes of pab1949 and a reference anti-OX40antibody pab1928 were analyzed by alanine scanning. The antibody pab1928was generated based on the variable regions of the antibody Hu106-122provided in U.S. Patent Publication No. US 2013/0280275 (hereinincorporated by reference). The heavy chain of pab1928 comprises theamino acid sequence of the heavy chain variable region of Hu106-122 (SEQID NO: 56) and a human IgG1 constant region of SEQ ID NO: 65. The lightchain of pab1928 comprises the amino acid sequence of the light chainvariable region of Hu106-122 (SEQ ID NO: 57) and a constant region ofSEQ ID NO: 25. Thus the heavy chain comprises the amino acid sequence ofSEQ ID NO:72, and the light chain comprises the amino acid sequence ofSEQ ID NO:59.

6.3.1 Epitope Mapping—Alanine Scanning

The binding characteristics of pab1949-1 and the reference antibodypab1928 were assessed by alanine scanning. Briefly, the QuikChange HTProtein Engineering System from Agilent Technologies (G5901A) was usedto generate human OX40 mutants with alanine substitutions in theextracellular domain. The human OX40 mutants were expressed on thesurface of 1624-5 cells using standard techniques of transfectionfollowed by transduction as described above.

Cells expressing correctly folded human OX40 mutants, as evidenced bybinding to a polyclonal anti-OX40 antibody in flow cytometry, werefurther selected for a sub-population that expressed human OX40 mutantsthat did not bind the monoclonal anti-OX40 antibody pab1949-1 orpab1928. Cells that exhibited specific antibody binding were separatedfrom the non-binding cell population by preparative, high-speed FACS(FACSAriaII, BD Biosciences). Antibody reactive or non-reactive cellpools were expanded again in tissue culture and, due to the stableexpression phenotype of retrovirally transduced cells, cycles ofantibody-directed cell sorting and tissue culture expansion wererepeated, up to the point that a clearly detectable anti-OX40 antibody(pab1949-1 or pab1928) non-reactive cell population was obtained. Thisanti-OX40 antibody non-reactive cell population was subjected to afinal, single-cell sorting step. After several days of cell expansion,single cell sorted cells were again tested for binding to a polyclonalanti-OX40 antibody and non-binding to monoclonal antibody pab1949-1 orpab1928 using flow cytometry. Briefly, 1624-5 cells expressingindividual human OX40 alanine mutants were incubated with the monoclonalanti-OX40 antibody pab1949-1 or pab1928. For each antibody, two antibodyconcentrations were tested (pab1949-1: 2 μg/ml and 0.5 μg/ml; pab1928:1.1 μg/ml and 0.4 μg/ml). The polyclonal anti-OX40 antibody (AF3388, R&Dsystems) conjugated with APC was diluted at 1:2000. Fc receptor block(1:200; BD Cat no. 553142) was added, and the samples were incubated for20 minutes at 4° C. After washing, the cells were incubated with asecondary anti-IgG antibody if necessary for detection (PE conjugated;BD Cat no. 109-116-097) for 20 min at 4° C. The cells were then washedand acquired using a flow cytometer (BD Biosciences).

To connect phenotype (polyclonal anti-OX40 antibody+, monoclonalanti-OX40 antibody −) with genotype, sequencing of single cell sortedhuman OX40 mutants was performed. FIG. 21 is a table showing the humanOX40 alanine mutants that still bind the polyclonal anti-OX40 antibodybut do not bind the monoclonal anti-OX40 antibody pab1949-1 or pab1928.All the residues are numbered according to the mature amino acidsequence of human OX40 (SEQ ID NO: 55). “+” indicates binding and “−”indicates loss of binding based on flow cytometry analysis.

The invention is not to be limited in scope by the specific embodimentsdescribed herein. Indeed, various modifications of the invention inaddition to those described will become apparent to those skilled in theart from the foregoing description and accompanying figures. Suchmodifications are intended to fall within the scope of the appendedclaims.

All references (e.g., publications or patents or patent applications)cited herein are incorporated herein by reference in their entirety andfor all purposes to the same extent as if each individual reference(e.g., publication or patent or patent application) was specifically andindividually indicated to be incorporated by reference in its entiretyfor all purposes.

Other embodiments are within the following claims.

What is claimed:
 1. An isolated vector comprising a nucleic acidmolecule encoding a heavy chain variable region (VH), wherein the VHcomprises the amino acid sequence of SEQ ID NO:
 16. 2. The isolatedvector of claim 1, wherein the nucleic acid molecule encodes the aminoacid sequence of SEQ ID NO: 21, 23, 51, 52, 60, 61, 62, or
 63. 3. Theisolated vector of claim 1, wherein the nucleic acid molecule encodesthe amino acid sequence of SEQ ID NO:
 21. 4. The isolated vector ofclaim 1, wherein the nucleic acid molecule encodes the amino acidsequence of SEQ ID NO:
 60. 5. An isolated vector comprising a nucleicacid molecule encoding a light chain variable region (VL), wherein theVL comprises the amino acid sequence of SEQ ID NO:
 15. 6. The isolatedvector of claim 5, wherein the nucleic acid molecule encodes the aminoacid sequence of SEQ ID NO:
 20. 7. An isolated vector comprising a firstand a second nucleic acid molecule, wherein the first nucleic acidmolecule encodes a VH comprising the amino acid sequence of SEQ ID NO:16, and the second nucleic acid molecule encodes a VL comprising theamino acid sequence of SEQ ID NO:
 15. 8. The isolated vector of claim 7,wherein the first nucleic acid molecule encodes the amino acid sequenceof SEQ ID NO:
 21. 9. The isolated vector of claim 7, wherein the firstnucleic acid molecule encodes the amino acid sequence of SEQ ID NO: 60.10. The isolated vector of claim 7, wherein the second nucleic acidmolecule encodes the amino acid sequence of SEQ ID NO:
 20. 11. Theisolated vector of claim 7, wherein the first nucleic acid moleculeencodes the amino acid sequence of SEQ ID NO: 21, 23, 51, 52, 60, 61,62, or 63, and/or the second nucleic acid molecule encodes the aminoacid sequence of SEQ ID NO:
 20. 12. The isolated vector of claim 7,wherein the first and second nucleic acid molecules encode,respectively, the amino acid sequences of SEQ ID NOs: 21 and 20; 60 and20; 61 and 20; 62 and 20; or 63 and
 20. 13. A host cell comprising anucleic acid molecule encoding a VH, wherein the VH comprises the aminoacid sequence of SEQ ID NO:
 16. 14. The host cell of claim 13, whereinthe nucleic acid molecule encodes the amino acid sequence of SEQ ID NO:21.
 15. The host cell of claim 13, wherein the nucleic acid moleculeencodes the amino acid sequence of SEQ ID NO:
 60. 16. A host cellcomprising a nucleic acid molecule encoding a VL, wherein the VLcomprises the amino acid sequence of SEQ ID NO:
 15. 17. The host cell ofclaim 16, wherein the nucleic acid molecule encodes the amino acidsequence of SEQ ID NO:
 20. 18. A method of producing an antibody thatbinds to human OX40 comprising culturing the host cell of claim 13 sothat the nucleic acid molecule is expressed and the antibody isproduced.
 19. A method of producing an antibody that binds to human OX40comprising culturing the host cell of claim 14 so that the nucleic acidmolecule is expressed and the antibody is produced.
 20. A method ofproducing an antibody that binds to human OX40 comprising culturing thehost cell of claim 15 so that the nucleic acid molecule is expressed andthe antibody is produced.
 21. A method of producing an antibody thatbinds to human OX40 comprising culturing the host cell of claim 16 sothat the nucleic acid molecule is expressed and the antibody isproduced.
 22. A method of producing an antibody that binds to human OX40comprising culturing the host cell of claim 17 so that the nucleic acidmolecule is expressed and the antibody is produced.